A smallish amount of rocks never hurt anything but normally they really are not what could be called a real plus either. Situations differ but that is pretty much the norm. If you have already drilled drain hole large enough that when runoff occurs soil might or will flow with it just use the minimal number of rocks of whatever the size you have/are using as it will take to slightly block the drain hole. If you have drilled drain holes that are adequate but not large enough for that to be the case, skip the rocks. If you have not yet drilled drain holes, drill them so you do not need rocks, but be sure there is adequate drainage.
Sorry if you mentioned if you have or have not drilled drain holes and I missed/forgot it, but sometimes that happens to us old guys.
I do agree with the advice about the 7-gallon pots over 5-gallon buckets. I tend to use 7-gallon pots inside much of the time and 15-gallon or larger were used when I used to grow on my deck. I am a very firm believer that pot size makes far more of a difference than some or many others believe.
While I would say use even larger than 7-gallon pots, a 7-gallon pot would be a much better choice, so unless you are locked into the 5-gallon buckets now, make the change. If you cannot change now just remember it for the future. It is worth it so plan for it and be ready with it waiting to be used next time.
If you continue to grow outdoors in pots you might want to consider the air root-pruning pots. When you have the proper size one of those the combination of enough soil and the way roots grow in them in comparison to regular pots, and since if the roots grow better so does the above soil parts of the plant, they are well worth at least considering.
With the strength of the sun for your lighting and the best possible root growth going, the results will more than make you smile.
