It depends what expansion packs you have.
If you have WA get yourself a holiday home and garden there. (unfortunately, the garden bug makes this impossible for an established sim)
Buy the gardening station and the (premium store content, currently only available with the whole greenhouse set). You get several perfect harvests per day if you want them.
Sell your produce through the consignment store, it's significantly more valuable.
Grow only life-fruit (by far the most valuable produce) and garlic to use as fertalizer.