Thanks for the fun challenge. Achievements were my mine focus when I was playing The Sims 4 right after it first came out, so I do have some experience with them. This was the strategy I used. Please feel free to ask if you have any questions. Sorry it's so long.
I started off by having my Sim make a garden salad and fill all of his needs except social to the top, and then sent him on a one day vacation to Granite Falls. With his needs at the top when he left, he wouldn't have to worry about them much while on vacation. His goals while on the vacation were to befriend the hermit, and gather the various plants that he would need later for herbalism, and to eat for the achievement Tastes Like Burning (25 points), which is to eat every type of toxic plant. After doing these things, I sent him home and had him plant the herbs that he would use later for herbalism, and then eat every type of toxic plant so that the effects would wear off while he slept and recovered from the trip. To assist with gardening, I set up an area for doing mental activities in the front of the lot, with a couple of focusing lamps for their aura effects. I continued to have him garden when necessary while he worked on other things. I also had him plant a parsley plant, which he got by ordering a seed packet, and gather wild plants around the neighborhood a few times, planting some sage, tomatoes, lemons, and carrots that he found. The main point of gathering plants around the neighborhood was to finish the achievement of harvesting 50 wild plants (25 points), which was started while on vacation. Once he reached gardening level 4, I powerleveled him to level 5 by having him talk to a plant. This was so that he could gather a snapdragon cutting from a different neighborhood sooner, which he could use to hybridize to his sage plant, in the process receiving the achievement for grafting (25 points). The purpose of this was to work towards making a cowplant, which involved hybridizing a few things and sometimes growing products of these plants. Growing a cowplant is a necessary part of the Freelance Botanist aspiration, which he did eventually complete. In the process he received the achievement for maxing the gardening skill (50 points).
After quickly doing the Basketcase achievement (100 points), his first activity that he worked on between gardening was making friends and building charisma. He was able to work on this on another lot while waiting for the snapdragon to grow. For some of my other achievements, my Sim needed to know people, so I figured I would have him make some friends at the beginning. In the process, he made a good amount of money by asking for small and large loans, and also a good amount of whim points, both through satisfying whims and completing the Friend of the World aspiration. He received the achievement for maxing charisma (50 points).
Next, I had him work on the Soulmate aspiration, in the process getting married to someone whom he had formed a great relationship while working on the Friend of the World aspiration. He had a gold wedding party, which would later be a necessary part of the achievements of completing five types of gold parties and five types of silver or better parties. His wife never moved in with him. He got a few achievements on dates with her while working towards this aspiration, including two hidden achievements gotten from having a bladder failure while on a date on a lot with five or more toilets, which was his home lot with four extra toilets added for the occasion. The achievements were No Excuse (10 points), and So... I'll Call You? (10 points). He also got the achievement for completing ten whims at a single social event (25 points).
By this point in the challenge, he had all of the perks that he wanted most, and was able to start buying moodlet solvers so that he no longer had to meet his needs the "normal" way. He was able to subsist off them, while eating a couple of carrots between them each time, so that he could wait until his energy drained before needing to use them. He also occasionally used the instant fun reward, if the activities that he was working on were not fun.
Next up was working on maxing the cooking (50 points), gourmet cooking (50 points), and mixology (50 points) skills. He also got the achievement of mixing 100 drinks (25 points) mostly through leveling mixology. In the afternoon, between the times of morning Sim and night owl, he would throw parties, in order to complete a few achievements. These achievements are Speed Dating (25 points), Event Horizon (25 points), The Main Event (100 points), and Host with the Most (100 points). Speed Dating is the achievement of first kissing with three Sims at a social event, which was the start of his deviant behavior. Event Horizon and The Main Event were completed at the same time by scoring gold in five different types of social events. These events were wedding party and date (earned while working on Soulmate aspiration), dinner party, house party, and incognito party. Host with the Most is the achievement for hosting 50 bronze or better social events. He got the remainder of these by throwing a dinner party, calling everyone to dinner, and then ending the party immediately, before anyone had eaten. Calling everyone to dinner is enough to make a dinner party bronze. To make this go faster and smoother, he kept one of his guests from leaving the lot by having her play chess. She was so enthralled in the game she didn't try to have dinner, or leave when the parties ended.
The next skill he worked on was painting (50 points), and completing the Painter Extraordinaire aspiration. During the afternoon he called his wife over for a visit, and "accidentally" left her swimming in a pool with walls and no door around it. When she died a couple of days later, he was able to befriend the Grim Reaper (25 points) just by introducing himself, thanks to the Incredibly Friendly reward. After this he built a rocketship. When his wife eventually came back as a ghost, they had their very first woohoo ever in bed for the achievement of woohoing with a ghost (10 points), and then woohooed again in a rocketship (10 points).
Most of the remainder of the challenge he spent completing the Nerd Brain aspiration, and maxing all associated skills. He made sure to read the required books during the afternoon, since it was a bad time for skilling. Maxing the three associated skills gave him 150 points, and Nerd Brain was his fifth aspiration completed, so he got the achievement for completing five aspirations of different types (100 points). He upgraded and instantly upgraded his TV and stereo, so that he had all channels and stations and was able to get the Channel Surfer achievement (10 points).
The only remaining things to do that took much time were maxing the herbalism skill (50 points), and the Old Lace Black Widow achievement (25 points). The ideal mood for herbalism is focused, which I figured I would mention since I could not find that information anywhere. It is a quick one to level by identifying the herbs, and then making the elixirs deodorizing cream up to level six, and clear mind distillation at six and above. He already had to identify the herbs before planting them earlier, so all that was left to do was make the elixirs. For the Old Lace Black Widow achievement, he eloped with four elders in succession, and then killed them by woohooing with them each two to four times in a row. This was the last of his deviant behavior. He then quickly visited the remainder of the 25 lots needed for the Knock, Knock achievement (50 points), and drank the reward elixirs to make him max fat and then max thin (25 points). He also met up with the hermit and asked him to move in, but then did not follow through with actually allowing the hermit to do so, causing a hidden achievement (25 points). Finally, it was time to celebrate his birthday and age up (10 points).
During the challenge, he also gained some achievements not mentioned above. He got the hidden achievement I'll Get Around to It (10 points) by buying ten cheap radios and turning them on. After a few days, they all broke at the same time, causing him to have ten broken objects on his lot and triggering the achievement. He earned the achievements for completing 100 whims (50 points), staying awake for 24 hours (25 points), not doing anything social for 24 hours (25 points), and having 12 or more traits (50 points) through normal gameplay. I also earned the achievements for playing for both 5 and 24 hours, giving 75 total points. I did not make it to the 100 hour achievement.
My Sim had the traits loves outdoors, loner, and neat. He started off with the Renaissance Sim aspiration, for the quick learning bonus. As his party attire, for maximum romantic success he used the Shine On Men's Suit and flirty cow hat, and wore them whenever he wanted to be flirty. At parties where he did not want to be flirty, he changed to formal wear.
