3 gallon is a good size, I personally like the 5 gallon buckets that you can get at Home Depot or any other hardeware store for like $2.50 a piece.
You will want to give your plant an all around nutrient during veg, something like 20-20-20.
Then in flowering boost the phosphorous up, so a 17-51-17 or something like that will do the trick.