This is a bit stupid tbh, you're comparing Everton signings to Wigan signings, of course Everton's will be better. Stones, for example, was pursued by both Moyes and Martinez but chose Moyes because he preferred a move to Everton, and I'm sure that's not the only time Wigan lost out on a signing to a bigger club.
While I agree with that to an extent, the problem is even for the level Wigan were at, Martinez's defensive signings were arguably terrible.
Look at it this way - Coleman £60k from an obscure team, Stones for a few million, Garbutt on a nominal fee, Lescott from the Championship etc. These are all the types of players Martinez could have reasonably signed for Wigan, yet didn't. Far from it in fact.
He deservedly has many question marks over his transfer market acumen for defensive players - and indeed whether he can set up a team to defend at all. Last season we were like a sieve at times, and that Arsenal game didn't inspire me with confidence that that's going to change any time soon.