There are 2 types of Bumgenius onesize nappies - the pocket nappies and the organic ones which you have bought.
The pocket ones have a waterproof outer and suedecloth inner, between which you put the microfibre inserts that you talk about which is the absorbent bit.
The organic ones have a waterproof outer and then the abosrobent bit is laid on the inside so you do not need the microfibre ones you have bought, although I guess you could add them to increase the absorbency
The liners you have are for catching the poo and putting in the toilet, although you could swap these for fleece liners instead which are washable and act as a stay dry layer.
In terms of wipes, you can either buy nice specially made wipes from places like Wee notions or you can just buy some cheap face cloths which work well and use either plain water or a specially made up solution you can buy
For a wet bag, check out the Wee Notions ones or the Blueberry ones, I know people have raved about them. I have a Mommy's Touch one which I really like as it has a zip closure and a little handle.
Hope this helps. Anymore questions just ask