With the terry squares you would obviously need some kind of wrap. Boots do the old style plastic pants, or you can bring things up to date with something like a Motherease Airflow which has poppers so much more adjustable - you will need different sizes though as baby grows.
I would definately recommend Nappy Nippas for holding the terries together rather than old fashioned nappy pins.
You might want to have a few extra boosters for overnights e.g. hemp or bamboo. But you can always use bigger terries or them up or use a muslin, or even an old owel cut up and hemmed.
You might also want to use a liner of some kind - flushable paper or fleece to catch the solids and make them much easier to dispose of. In the early days of liquid poo a liner wont make much odds and you can just chuck it all in the washing machine (honest!). When it gets more solid then having a liner will probably make more sense. I use fleece (keeps the wet away from the skin) and I just used a cheap fleece blanket cut up in hourglass shapes.
You will probably want to have a waterproof bag of some kind to store dirty nappies in when out and about, with a zip to keep the smells in. You can buy them in different sizes, or look for an adequate wash bag.
A nappy bucket is of course essential, try and get the biggest you can - at least 14 litres. No need to saok nappies, just dry-pail and wash every 2 days at least. You can add some tea-tree oils to the bucket to keep smells down.
Finally washable wipes are a no-brainer when you are already washing nappies. As others have said cheap flannels do the job well. IKEA do a cheap pack of 10. I find I only use 1 per change (use loo paper too to remove the worst first), they have much more surface area and friction than a paper wipe. I use tupperware which holds 10 flannels comfortably and pour over a cup of chamomile tea with a little squirt of baby wash and sometimes some tea tree oil. You can take them out on the go in a ziploc bag.
Hope this helps!