If you don't want your sim to be a gardener and just want the life fruit alone, I would have the spouse do the gardening, instead. Easiest, imo, is just handing them the gardening skill books, maybe give them the bookworm and green thumb trait if you have time to give them a Midlife Crisis LTR. If you don't know where most of the special seeds spawn in your area, then get the collecter finder/helper one instead. Only focus on collecting special seeds, unless the gardening skill is something you want to max out.
Once you hit level 7 or so and after a couple days of collecting (I say start the collecting early asap, and just worry about the actual planting a little later but not too late). Plant all of them, and then buy some of the planter bowls early if you have Supernatural. Go to buy mode, move the plants over, and you'll see that some of them won't fit, because those are money trees. This is an easy way to figure out a little early what plants have the highest chance of being life plants. You will also need some death flower bushes, and I believe the green thumb trait comes in handy for this, as you can have a chance at reviving them and getting more produce.
The planter bowls are even extra useful if you have Seasons, as plants have a tendency to go dormant in late Fall, Winter and Early Spring. You can always adjust your seasons to your advantage, but better just to have some of them inside, if you can.
If you have money, go ahead and buy a good amount of lobsters at the supermarket. Lobsters make good temporary fertilizers, and while it won't mean much if you don't have a gardner in your first gen, you can always pass down the higher leveled quality fruit to the immortal you plan to inherit the gardening career/supermax trait. Becareful once you harvest some life fruit, though. They make great fertilizers, and your sim probably will use it automatically if you choose the "fertlize garden with best fertilizers" option, unless you got something of even higher fertilizing strength. So temporarily take away your life fruits from that sim, when you do that.
I had logic as my first gen's supermax skill, but that required a LOT of planning and the spouse pretty much had to do everything. Didn't turn out to bad, considering, though.