First you mention your on a budget but then your next plan is to go out and buy hardline and an amplifier which cost a lot more than what you already have not to mention you will probably need a new power supply for the amplifier which will most likely not help out a bit except for reduce your isolation and increase your frustration level.
Also what about an isolator on the transmitter output, do you have one, you'll need a LPF after the isolator and what about your cavities who is tuning the duplexer for you ?
If your doing it yourself then you need a good SA with tracking generator and remember that the cavities really need to be fine tuned with everything connected and well grounded, and you can't get away with any type of crap cable, even for the in shack interconnecting cables.
You'll need a controller with proper ID and what about lightning protection, proper grounding at the antenna and cabling, the use of non NICKLE plated connectors, do you know about these important aspects of repeaters ?.
Without any of these being considered then your just asking for PIM problems and/or constant noise getting into your system which comes back to your frustration level going through the roof.
Before you go any further stop and think about spending any more money to put up a repeater that will most likely only work a mile or 2, I have seen to many backyard repeaters that turn into money pits and frustration.
Save your neighbors, wife, parents or whoever the constant swearing when your repeater doesn't work and your antenna keeps falling down and do something sensible like joining a local radio club and volunteer to help/be mentored on their local repeater, this way you'll learn what's involved on keeping one on the air.
Which brings up another point that others are trying to get across to you, I hope you aren't expecting to simply put it on the air and then not have to work on it after that because I guarantee that you'll be constantly working and maintaining it to the point where it isn't fun anymore, after about the first week you'll want to tear it down and toss it all in the garbage.
If you have the patience and your wife or parents don't kill you from constantly going up and down on the roof to fix the antenna or slamming the door when going from the antenna to the duplexer room to tweak the cavities and the constant cussing because the stupid repeater doesn't work or it keeps blowing squelch, then maybe you'll learn something but I'd really suggest stopping before you waist any more time and money.
Been there, done it with a SO 155 MHz rptr, a ham 900 rptr, a ham UHF 440 rptr and a ham 6 meter repeater take my word for it, it isn't fun doing it alone.
Mike
