Exrivofrigido is referring to PCCBC, which you should attend prior to starting the Commissioning Course. It's extremely useful, I attended the November one and feel much better about Sandhurst overall (less nervous, more excited) since doing so, and now have the chance to wear my boots in!
I don't think that UOTC members "transfer" to the Regular Army - I believe they join it.
You'll have to waterproof your maps. You can just use a map case if you want, but I found fablon to be a lot easier to use.
You will also be given lots of little cards, and it's handy to get them laminated so you don't destroy them. Off the top of my head these include cards with correct VP, platoon quick battle orders, range cards, serial number cards, qualities of leadership card, and many many others. Laminators are not expensive (mine was about £20), and they will save you a lot of hassle.
However, listen to everyone's advice and don't buy anything for the moment.
Oh, and please don't ever refer to leaving University and joining the Regular Army as 'transferring' ever again. Because you will be ripped to shreds for being an arrogant fantasist. UOTC is a college society.
Just Fablon the sh!t out of everything - or just use your tams (if they still exist) or write it down in a waterproof note - much easier than having tones of fcking cards falling out of your pockets or breacon pouch making you look an utter gangfcuk - or you could do that novel thing & just learn it!!!
Bottom line the only thing you should fablon/laminate is your map.
Again, don't (well, take the grot, obviously). You may be allowed to use it, you may not. TAMs and waterproof paper are encouraged rather than Nyrex - Pl Comds shouldn't need to carry vast reams of paper in the field, but you will need to write in the rain! Either way, save your money until you've been briefed properly on the PCCBC. Most of this stuff can be had at the Ac shop, and prices are reasonable now they've been beaten into line with the competition.
Plenty of good suggestions above, but you really do need to get through the first few weeks before you start experimenting. Chances are, if you spend money now, it'll be money wasted. Fablon should be issued in reasonable quantity (enough for a couple of maps if you really won't use a map case). Not having a laminator is a minor inconvenience in the great scheme - you can usually share.