sorry for the long delay but I had to work a lot lately.
I posted the said multitracks for everyone to use with a description here: https://www.producelikeapro.com/forums/topic/free-multitracks-working-with-less-than-ideal-recordings/
To your questions:
The first big hurdle is to realise that you aren't working with top professionals most of the time! You have to stay positive and encourage them while also giving tips to improve to after all getting the best performance possible. That doesn't mean it is perfect, so learning the basics (and later advanced stuff) of how to fix timings and for a singer also fix the pitch to get a good more professional sounding raw record is key! I don't think most of the videos out there for correction are good. They always seems like giving you a tool for easy correction just pulling it to the grid. BUT this is wishful thinking that music will sound better on a grid. You need to practice where to put transients that the performance sounds human, with good timing and with as less artefacts as possible. This is a lifetime of work to master! The same for pitch correction. There is no skill ceiling, you can always improve on them!
After that you can start working on your mixing effects. For me I try to make the mix sound as natural as could be and I use so much unnatural tricks to achieve a good natural sound. This is pure experience and knowledge. (One example for knowledge is a trick Warren uses all of the time (me too xD): having the close-recording on one side and the verb of it on the other side to give it a more 3D sounding feel (if a guitar is near you on the right side the first verb reflexion you will hear comes from the left side so its an unnatural imitation of a natural phenomenon).
And the last of the "first" hurdles to overcome is: knowledge and experience is key, gear is not! for sure a new preamp or a new plugin is nice to have but first you should be good with the things you have before you start getting to know new stuff! I wasted so much time and money on getting new plugins and stuff to overcome my insecurity and incompetence I could have invested in so much more stuff that really would have helped like basics!
I stop here as I could write for hours about this so I will stop here ^^
If you have more questions just ask and have a good time producing, recording and mixing!