Peapods are a good cheap nappy! I have 4 of them but there are better ones out there IMO I would advise you to try few different ones JIC the cut of the nappy doesn't suit your bub. It's amazing how they differ.

With pocket nappies the whole idea is that the inner layer acts like a liner and lets the moisture pass through the booster without absorbing so the bott stays dryer.
The wicking effect won't work with two layers though. It will be too thick to let the wee through and it will just run out the leg.
For runny poo a little rinse in the laundry trough or a little squirt in the loo gets it off before the wash. Solid poo just comes off in a clump!

I understand your apprehension about the cost outlay. I was the same when I started using MCN but I'm doing this for my third child. The other two were mostly in sposies and it's cost me at least $5000 ($1000 per year per child) as Mason didn't TT till he was 3 1/2. That is something to baulk about!