The one thing to know is that wicking is the biggest difficulty in RTA's. Finding one that's easy to wick would be recommended to start. Making coils takes a little practice as well but you can vape on less than perfect coils. But, if you don't wick right you'll either get dry hits (too much or poorly placed cotton), or have the juice simply leaking right through the system (not enough or again poorly placed cotton).
There are a few different styles of wicking. The Goblin Mini (i'd get the v2 at this point) has a very easy wicking style that it shares with the Diablo RTA (one of my favorites). Likewise the Boreas is probably the easiest wicking I've dealt with, sharing the style with the Aromamizer and Aromamizer supreme. The Griffin is a more standard style of wicking, I wouldn't say hard but might not be as good of a start. If you're ok with a beast sized tank the Boreas would probably be the easiest to start, huge deck and easy wicking (though refilling has a process you need to follow). If you want something a bit more compact the Diablo RTA is great. Hardly your only options though.
(If you do go with the Diablo, if you want adjustable airflow the smaller size clone is your go to, the larger size has no adjustment option).