I want to try my hand at developing my own package, is there a good way to isolate my development of the package from emacs, so they don't spill into my current emacs session?

you could run it with just -Q or you could use your own init just for it using https://github.com/plexus/chemacs

hmm, well I want my original config I just want it so whatever i eval in a buffer can only be called within that buffer.

i guess something like a sandbox mode for a file.

That sounds like a separate process then. Emacs lacks namespaces much less sand boxes

I figured, a new instance should be fine