you should get 7 grams off a good side limb. Your top cola with most medium to high yeilding strains should weigh AT LEAST 1/2 oz dry If you're doing everything right, and you let them veg for a month to 6 weeks. All that transplanting you're doing is kinda pointless IMO. Why not just put the put the clone in the 5 gal. pot after it has good roots? Even the 1 to 5 gal. is fine. If you have the space already, put them in the pot you're going to finish in. You're just risking shock for no reason. What are your temps at if you're running CO2? How long are you vegging your plants for before you force flowering?
Ok you could improve by A : using a metal halide for vegging if you can. CFL's are good too because they seem to give my plants tighter distance between nodes with makes for a more compact plant which = more bud in less space. Maximize your yeild for your space.
B: Don't transplant as much, there really isn't any need for it unless your area isn't set up, and you currently don't have the space, or have the space dedicated to something else.
C: If you're using CO2, it's more effective with higher temps, (mid 80's to low mid 90's) Your area needs to be sealed as good as you can possibly get it.
D: Get a good strain if you don't already have one. It helps.