You could put it into a small window plant container, however, you want a nice root ball, so the more space you can give the roots to shoot out you will have a more stable plant and wont have to worry about root problems. You will know when the plant needs more root space. Keeping in mind that a plant will start shooting up when the roots can not go any deeper. My plants are about 4 inches tall and i just planted them in a size 5 pot. the plants have anywhere from 4-5 sets of leaf's on them.

One last thing, there are several people on here who have several posts, what i have done is gone and read some of the grow logs and noticed that there are certain people who know what the hell they are doing and are REALLY REALLY good. Once you figure out who you like and their style, look for their posts, you can find alot of the answers you are looking for by reading what they have posted already. Personally one that i follow closely is Stinkyattic, she knows what she is doing.....

Hope that helps