They might not be doing great on the pitch but that's not mainly down to the sort of players they've signed. More to do with the management changing too much after promotion.
They haven't broke the bank for anyone and don't pay massive wages, when they were in L1 they spent fees on good young players without going crazy, and it worked very well. Look at Wildschut, signed for £1m and they sell him a year later for £7m. Then look at Morsy and Power who are both doing well in the Championship. Alex Gilbey's also an excellent signing in midfield but is currently injured. They've done very well to get Bogle.
They've currently got 9 loans though after going mental yesterday. That's not too wise.