I've never seen Banega as a DM, he just doesn't have very good defensive stats. Could buy a tackling DM like Jean II Makoun and play Banega as CM? Makoun costs in the region of 11m and is really one of the best buys you can get early on. Song and Diaby both seem to leave Arsenal as soon as they start spending money on better midfielders, or maybe Lucho González (good hard-working midfielder with a wicked shot) or Luka Modric (extremely versatile, plays holding role pretty well).
At right-back you ideally want someone fast, with some bite. I've been getting use out of Justin Hoyte, very quick on the flanks with a good tackle. Samba and Ignashevich have both been starting right-backs for me at some point and both did well.
If you're playing 8.0.1 Aaritolo isn't
prem quality, but if you're on 8.0.0 I assume he'll be good enough. Farfan and Ménez both offer great options as wingers and second strikers, Farfan being a class act capable of going straight past some good defenders before crossing or shooting.
Up front you'll be fine. Yakubu is pretty prolific, and Briand and Johnson are both quality too. It's worth pointing out that Vaughn becomes a class act a few seasons in, and Baxter in your youth is your biggest bet for the future.
If you're really worried about a goalie, you can get Bogdan Lobont at the start of the season for a bargain 3mil, or Vicent Enyeama for usually a million in the january window (more expensive + hard to lure away at start). Of the two, Enyeama is an extremely good captain with perfect reflexes, so I'd reccomend him.