First build

...Also as I've never built up a bike before any opinions as to how I can do it while keeping the costs from spiraling while balancing the need to make the build as straightforward as possible would be appreciated...
Reusing the parts you already have will keep costs down and help keep the build as straightforward as possible.

Avoid getting parts removed from, or added to, the frame unnecessarily; this will keep costs down and and help keep the build as straightforward as possible.

Know what the frame was intended to be used for and keep that in mind: the further you stray from the original, the more expensive and complicated things will become.

Build first, paint second: you want to make sure everything fits and works before the frame has a new coat.

Don't bother getting it painted.

...Promise this is my last question. For a firsts build would you opt for a kit consisting of wheels, crankset, chain etc. try to source 2nd hand or buy parts separately?
Don't be daft: if people didn't ask questions, there'd be no forum!

Buy parts separately.

First though, you need to post some photos of the frame and list what components you have.