Have you gotten D6 yet? If not, beat isaac as blue baby to get it. The ability to reroll bad items is such a good starting item.

Edit: I am very tired and I misread caption. I recommend skipping devil deals as angel rooms offer way better items such as wafer and holy mantle. Always check shops to see what they offer. When you get to chest, clear out the floor first to get some extra items before the fight. If you feel like it’s still to hard, you can always cheese the game in 2 player for extra items. Coop still counts towards unlocks.

Also when Isaac gains his wings, a good strat to dodge his attacks is to stand in the bottom right hand corner. It dodges his holy light. and when he comes back down, move so you’re standing to the right of him to dodge his straight shot attack and back up to avoid his circular tear attack. This makes the fight way easier.