Having just started myself, I don't have much advice for you but can say that we are still in the very early stages. So you definitely haven't missed the boat.
I have actually been thinking of building a 6-8 GPU mining rig but with the inflated pricing right now that is a very expensive endeavour. Might hold out and wait for the prices to come down once more cards hit the market.
Thats my problem, GPU's are way over priced right now or not in stock.