i'd say start with something that's more indica or indica dom, as heavy sativas can be tricky to grow, even for non beginners ..
secondly, don't go off of what a breeder tells you in terms of expected yield, thc percentages, grow times, etc, etc.. not to say breeders lie, lets just say they tell what the best results could be under optimal conditions..
also, try not to get too caught up in what i refer to as the flavor of the month club. it's tough at times being a newbie, and either seeing or reading about all of these new cool strains out today, let's say that super og gorilla glue lemon haze that's in all of the magazines.. not to say that these can't be good, just that sometimes they're not the most stable strains out there, and a lot of times, they don't live up to the hype..
lastly, where to order.. check out some of our site sponsors, or look in the seed bank review section on here for some trusted places to order.. where to order depends on where you live.. there's tons of euro based banks, some have better stealth that helps get them through customs if you're in the us of a, but in the last few years, that's a ton of new us based banks, that, although, usually don't have as many breeders as many euro based banks do, you don't have to worry about spending all of your coin and having them get snagged in customs as they ship right here in the states, and therefore customs is not an issue..