LOL, the list goes on and on. Since you you're getting your armor in a month, I would suggest getting your supplies and tools first (mentioned in above posts). It took me a couple of months to get the armor built so maybe order your belt and holster when you are planning on working on the belt (usually towards the end). The gadgets and blaster you can save for last.
What I recommend is looking for deals in the craft stores like Jo-Ann's or Michaels when getting your elastics, e-6000 and or scissors etc, they almost always have 40-50% off coupons. Harbor Freight has pretty cheap clamps and tools.
What should have been my first suggestion is find builds based on your armor and follow them so you can have it saved, study what you will need to do in order to reach IEB status and Centurion, lots of research.
Lastly, if you have any loved ones, talk to them about this little project. I've been grounded from my build by my wife and kids for spending more time on it than with them