I would not recommend trying the Townie Decadynasty with only the base game, mainly because you might not be able to supermax the guitar skill. I would also recommend having 3 neighborhoods and taking advantage of the ability to move twice. Here's my review of the various EPs -- with regard to the Townie Decadynasty only.
World Adventures -- Good. Adds 3 skills (but they can be difficult or buggy to supermax), new plants and fish types to help with supermaxing gardening and fishing. Adds Tourist and Explorer to list of NPCs. Adds Black ops that require travel, and you may use up to 3 adventures as Black ops. Provides time in which to work on skills.
Ambitions -- Excellent. Adds a new neighborhood, 2 skills, and new jobs, including the self-employment careers. Adds the Consignment Shop. Of special note -- all the cases in the Private Investigator profession count as Black ops.
Late Night -- Good and bad. Adds a new neighborhood, 4 skills (but don't try to supermax the instruments), and 3 careers. Adds mixologist, butler, bouncer, and paparazzi to list of NPCs. Adds Black ops for the skills and careers, including celebrity ops. Downside -- adds vampires, which can make spouses ineligible, and celebrity status, which can cause your sims to lose their best friends.
Generations -- Good if you're writing a story, as it adds more gameplay for toddlers, children, and teens. After school activities add a few Black ops. Adds party dancers to list of NPCs. The Young Again potion is useful for fiancees who become elders before you can marry them.
Pets -- Good if you're writing a story. Adds a new neighborhood, a new skill, and a new career. "Best in the Show" is the only new Black op I know of. Minor pets can be used for collections.
Showtime -- Good if you're writing a story. Adds a new neighborhood and 3 careers that provide a few Black ops. Adds proprietor, singer, magician, and acrobat to list of NPCs.
Supernatural -- Very Good. Adds a new neighborhood and a new skill. Townies who become fairies, vampires, and werewolves will live longer and can be transformed into humans (or witches) with a Potent Cure Elixir so that they can be used as spouses. Adds friendship, skill-boosting, and invigorating elixirs.
Seasons -- Good only if you're writing a story. Holidays, snow days, and sick days in spring and summer when you can't get a flu shot threaten your heirs' ability to make the honor roll in elementary school. Cold weather makes gardening difficult unless you have the Greenhouse or plant bowls from Supernatural. Wildflowers and festival eggs can be used for collections.
University Life -- Very Good. Adds 3 skills to supermax and 3 careers. Adds mascot to list of NPCs. Adds a few black ops, and you may use up to 3 university dares and jobs as black ops. Time spent in University gives you time to work on a skill, and a degree starts your sim at level 3 of a career. Possibility of adding 1 or 2 new traits. Red berry coffee bean is a lucrative crop if you're a self-employed gardener.
Island Paradise -- Good. Adds a new neighborhood and a new skill and career. Diving work adds 7 Black ops, and you only need 2 skill points in diving to be eligible for them. Shells can be collected. Downside -- you have to live in Isla Paradiso to benefit.
Into the Future -- Good for one or two generations. Adds 2 new skills and 5 careers. Adds Time Traveler and Plumbot Waiter to list of NPCs. Nanites can be collected. Adds some Black ops, but severely limits your ability to pick up skilling opportunities. Time spent in Oasis Landing is not free -- your sim will continue to age there.
As for premium content, I would strongly recommend the playpen, which can now be bought separately from Aurora Skies. Your toddlers will pick up one point in Charisma (which can be activated by a short speech with the mirror), and add to the Logic skill they gain from the peg box. As long as they're talking to the mirror or playing with the abacus, their needs will be filled.
The Multi-tab cuts down on the time your teen needs to spend on homework. It should be kept out of the hands of former heirs, though, because they can easily max a skill that another heir has supermaxed.
The Basketball Hoop is highly attractive to Sims, but a danger if one of your heirs has supermaxed athletics.
I've not had much success with the Greenhouse, but the Gardening Station is a boon for gardeners and also spawns special seeds.
The Harvest Stands are now available separately from Monte Vista and provide 2 new plants plus a place to buy life fruit.
