Doing it on a loop is harder even if you have every single advantage, Ark 2-3 is no joke.
(I miraculously completed it on loop 4 on my first save file and in an hour completed it on a non-loop run on my second save file with no sweat)
Fishing material (you can complete first two floors just by using the base four babies so the focus is on Ark 2-3):
- Lil Loki is a solid pick since it can not be stolen by hands.
- Bob's brain is essential pretty much: against mulligans, whales and unexpected breaches.
- Deserters can be nice at the start of Ark 2-3 (and OP before that) since only 2 of them cover every line and destroy basic mobs with AOE;
- Blue Candle can empower Deserters with blue flame and they spread that blue flame to each other, so they might be more useful (this combo alone can carry you up to Ark 2 even on a loop; you probably do not even need the combo if you are not looping).
- Imp is OP if you are lucky to get one from Mystery Gift since it costs 0.
- Ghost baby is strong, but as any other fire power you are likely to lose them by the last wave due to hands.
- Blanket and/or Book of Shadows can help secure some fire power.
- Sanguine Bond is really good to place cheap spikes with Cube of Meat;
- Isaac's Fork is OP here to have some hearts going, but not essential, Red Shovel can be also of help since you do not usually want to have blow up material near the entrance and it saves you some hearts if you are removing Cube of Meat.
- Chargers can win you the last wave of Ark 3, just save them before that.
- Salvation effectively gives you free chargers so you can be more flexible with your defense on last wave.
- Glowing Hour Glass is all round best defensive and disaster-preventive active item; you can make enemies walk over your spikes twice, remove a sneaky bastard on that one line away from your charger or prevent an explosion, etc.
- The Black Bean is cheap and flexible source of AOE damage, can be helpful to weaken waves while feeding whales with bob's brain or placing Sanguine Bond's spikes in the process.
- Notched Axe can help you destroy "stoney bois".
- Poke Go is really good, basically a free utility on cooldown.
One timers like Snowball and BFF are a waste of space and hearts, do not use them.
TLDR:
On a fresh run fish for: Lil Loki, Imp, Deserter + Blue Candle, Ghost baby, Blanket, Book of Shadows, Sanguine Bond + Isaac's Fork + Red Shovel, Salvation, Glowing Hour Glass, The Black Bean, Notched Axe, Poke Go. Take Bob's brain. And avoid Snowball and BFF.