Good costume is a difficult one but there are vast repositories of kit available on internet, or if you are handy with a sewing machine from the charity shop and from fabric sales. Armour and weapons will basically have to be professionally made but most other things can be obtained for reasonable cost if you know where to look. Knowing other Larpers is obviously a bonus as they will help you out but failing that a simple Google search will turn up all kinds of Forums and websites that will help you out.
Rising of Chaos itself has a fantastical environment so pretty much any inspiration can be drawn for your concept design so long as it doesn’t really exceed the renaissance period: Knights in armour, robed wizards, tribal’s clad in fur. You can find pretty much anything depending on where you want to look. It’s best to familiarise yourself with the background of the system before making any firm decisions and of course you can always e-mail or phone for help.
All players, be they big or small, male or female, human or troll should carry some form of Physical representation (Phys-Rep) for any kind of item that they are carrying. For example if your character is wearing armour then you are wearing armour, if your character is carrying a potion then you must have a bottle to represent it, you savvy?