Depending on the type, seed packs can be a bit pricy, but you only need one to get started. These can be purchased from any computer if your Sim doesn't have a computer of their own, they can be bought from the public computers at the library or through gardenening pots. The immediate cost all Sims will need to make is a starting pack of seeds.
For this reason, it's paired well with the Fishing skill, as fishers can use the fruits and vegetables for bait, or gardeners can use fish as fertilizer for their crops. Even better, as long as you care for your plants, they will grow forever you won't need to worry about soil rotation or anything that complex. If you plant outside, you can do so directly into the ground. However, garden pots are only necessary if you wish to grow crops indoors. You can purchase 'Garden Pots' from Build Mode in Function Sort > Activities and Skills > Outdoor Activities. Gardening has a fairly low starting cost depending on the size of the operation you wish to run.
