As far as fruiting plants indoors go, I recommend ground cherries (the Aunt Molly's, Goldie, and Ammon Martin's types). They fruit pretty easily indoors. I've never actually tried growing them indoors beyond the seed-starting stage, but when I started them super early, they did fruit indoors (on south window light) before the transplant, without trouble. Tomatillos, on the other hand, don't fruit as easily indoors as ground cherries (some people call ground cherries tomatillos, so don't be confused by that).
Watch out for things like spider mites. They didn't bother mine indoors, but they sure did outdoors (peppers seemed the reverse; they seemed to bother them indoors but not outdoors).
For herbs/greens, I might recommend trying green onions / scallions (for the greens; not for the bulbs). Actually grow them in soil from seed (not in water from grocery store scallions like they say to do online; they do actually need nutrients, and growing grocery store produce can be illegal in some cases).
As a herb, you might also try a makrut lime (Citrus hystrix). The leaves can be used in cooking. I haven't grown a makrut lime tree, but I have grown citrus trees.
A lot of people recommend basil and mint for indoors, but I don't personally.
For houseplants, I recommend these:
- Spider plants (Chlorophytum comosum; these plants are very rewarding, I think; they make the air smell good if they get enough sun, water, and growth; the plants grow a lot more vigorously with more sun, but people tell you to avoid that so the tips don't burn; however, it's not the end of the world if the tips burn; you can trim the tips off and they'll grow new leaves; they also grow more spiderettes with more sun, and the plants develop more growth points in the soil more frequently; they grow bigger in bigger pots, if they have enough sun; however, people often like to put them in hanging baskets or lower light where they don't grow to their full growth potential)
- Golden pothos (these are lot more rewarding if they're not in a small container, because they grow faster and don't get stunted as easily; they don't need a lot of light to do well, but don't neglect to water them when they need it or they may lose leaves)
- Thanksgiving cactuses
- Stapelia (don't get one of the more difficult species of Stapelia to keep as a houseplant; these are attractive cactus-like plants that grow cool flowers; they're not cacti, though; my grandma had one in an eastern windowsill, and everyone loved it; it never had the smell people talk about, as far as I know, though, but it had big flowers)
- English ivy (most people grow this outdoors, but it makes a good houseplant; make sure your plant is disease-free, and ideally not taken as a cutting from an outdoor plant, since it might have diseases and/or pests)
- Tradescantia (the solid green vining type is really cool for a houseplant; to get it to live for a long time without taking new cuttings, you may need to do some research)
- Fittonia
- Geraniums (I forgot which genus I mean, but some plants known as Geraniums both flower nicely and make decent houseplants if you have a reasonable amount of sun; the leaves smell good, almost like carrots.)
- Arrowhead plant
- Philodendron hederaceum (Heartleaf Philodendron; these are kind of like a golden pothos with smaller, but solid-green leaves, and faster growth, with sheaths)
One thing you really need to remember is that the smaller your pot is, the faster the soil will dry out, and the more drought-stress a plant will experience if it does dry out. It's a lot easier to kill a plant in a small pot because the drought does more damage. A lot of people will warn you not to make the pot too large for the plant, but they won't tell you it makes plants more finnicky and makes them so they don't grow as big; you can always plant multiple cuttings in a larger pot to compensate for smaller plant size, if you want the benefits of a larger pot without having it be too big.
Problems with pots that are too big include these:
- Uneven watering (if the plant has been freshly transplanted, it needs frequent moisture where the roots are—not simply in the pot; for new plants you'll probably need to do frequent light waterings, such as with a thin spout)
- Some plants, such as snake plants, are said to prefer a tighter pot (perhaps to help them grow more evenly and upright); snake plants are popular, but I didn't mention them above since I consider the ones I did mention above easier to grow.
Some houseplants you might consider that I haven't grown are these:
- Chinese Evergreen
- Cast-iron plant
Some plants you might try if you're adventurous, but I don't really recommend as easy plants include these:
- African violets
- Aloes
- Snake plants
- Orchids
If you want a big plant, you might try an umbrella tree or a rubber fig, but there are special things to know about with caring for them:
Rubber figs seem to like frequent waterings, but not lots at once; they don't like frequent changes in their light levels; don't move it to a new location often; let it adjust to each location before moving it again, and ideally don't move it at all. You might need to stake them.
Umbrella trees might be more touchy about nitrogen fertilizer, but are otherwise easy to care for (you might need to stake them).
Many kinds of cacti make good houseplants (I don't know the binomial names for all of them), but if they have thorns you might get them in you on mysterious occasions for no apparent reason. I had a cool big cactus once, but we had to get rid of it, because it had large thorns (about 1.5" long) that seemed dangerous (I woke up with one in my abdomen one time). It was a great plant, though. I think it was some kind of prickly pear.
