Dreamscaper

To do this you will need enough bombs and keys for each floor. RNG will determine that, along with how many you have upgraded to start with, BUT there is also the factor of finding the secret rooms to reach 100%. To easily find secret rooms you want Xray glasses (which has to be unlocked before it can be found, and you have to find the idea before it can be unlocked...).

You do not have to destroy everything to get 100% on a floor. Just need to visit every room and you can't skip bosses.

To find secret rooms without the glasses can be annoying and usually luck based. Using a bomb in the room will cause the secret room direction to glow/shimmer. That means it can take up to 2 bombs to find. Xray glasses require 0 bombs to find. Also, your best bet is to look in areas where 2 or more rooms connect. The more the better odds its there. A good suggestion, if using the bomb way in stead of Xray glasses, is to wait until you clear the level then go back. If you've bombed a room before then it leaves a weird marker that shows. So if there is no shimmer there then it wont be connected to any room connected to that one either. Meaning if the empty space was to the left, and there is a room below that, then said room below that wont have a secret door facing upwards either. This can help narrow it down.

DEDLY CUKE makes an excellent point that you can, and should, upgrade your starting bombs/keys via meditation. This, with Xray glasses, will make this achievement much easier.

Final note - Secret rooms are never connected to boss rooms. I hope this tid bit helps.