Assess the squad, selll dont fit, you want out, get in who youwant/can get, play to their strengths. Then target players you want who can bring something more finesse, marquee, more in line with what you want without compromising the balance and ethos of what got you there.
I know I go on about Arsenal but as great as Wenger is, he compromised on the squad strength to play pure football which in such a hard league, physically, has cost them. If, like Ferge, he replaced the vieras, petits like for like then they would have won so much more. Fergie always plays to tthe strength of his team, hence why, despite being poor squads by their standrds,manure still win things.
Know your squad. Know their strengths, weaknesses. Play to that, then change things slowly over a position of strength.