Gardening is no more a gated content then Coil is. Coil requires that you have at least one level 50 battle job and that you have a certain amount of gear, if you do not put this minimum amount of time and effort in, you simply are NOT doing coil.

Gardening is similar. It requires you have at least one gathering or crafting job at level 50 and that you spend a certain amount of time trying to make gil. If you have a level 50 gatherer, even if its not melded, and you use that job effectively, you can make 2-4 mil gil pretty easily. Crafting is even easier to make gil but it requires more economical knowledge, research, and some investments. If you are just gathering "casually," then it will take you longer but that is YOUR choice. Even if you have a job or whatever, your time is not any more valuable than anyone else's, you should NOT be getting the same treatment as those who have put more time into the game. As long as you keep at it and save gil, which is ridiculously easy to do in this game since there's nothing else to spend your gil on, you will slowly but surely get there. This is assuming that there will be enough housing space to go around, which I admit is not a safe assumption. If you're just gonna sit around, expecting housing and gardening to be given to you as entitlements that you're simply not gonna get them or at least do not deserve to.

There are other ways to get gil besides gathering and crafting but if you are doing thing legit, they are probably the longer routes.