Another flats fan here!
I wouldn't bother with anything other than 60cm cotton squares at least for daytime. Thinner ones for littlies (cheapest of the lot) and then thicker for when they get bigger. I really like the most basic Junior Joy ones, and then Terry Tots with the binding around the edge - cheapest to buy from realterrynappies. Bright Bots are also good, and it's fun to have the different colours. We used an origami fold early on and have now moved on to a kite fold.
Over the top we've really liked the Nature Babies adjustable wraps (poppers on the rise and then applix fastening), but I've just ordered some blueberry coveralls to try out, which also get great reviews. I also use Nature Babies hourglass shape fleece liners. That lot, plus a wet bag and a few nippers you're good to go
For night-time we mostly use bumbles, boosted with 40cm bamboo squares.
Advantages for me of cotton over bamboo is that you can wash it up to 90 (not that I do), and then dry it on direct heat (radiators) if you need to. Flats in general are great for absorbancy, fast to dry and just so straight-forward. No faffing with inserts and boosters and what have you, Plus super-cheap
Nest shop have a couple of kits, as do realterrynappies.