Well an AEG is not that complicated once you understand it ( I am no expert btw.) .Now a gas blow back rifle as far as I know has more moving parts which means more possibility of something breaking. For a beginner's gun an AEG if defiantly the way too go. If you still want realism there are blow back AEG's but I have not heard much about them personally.
Anyway good luck with your first purchase =) I would suggest 007airsoft as Ken is a great guy to deal with and will look after you . So is Frank at velocity arms too. Both great retailer's.
Primary- SRC G36K
Secondary- KJW M1911A1