These sort of things usually depend a lot on one's taste but I'll drop a few that I really liked.
RE: Trailer Trash - Amazing writing and an equally amazing main character with very human motivations. Watching her change her life slowly but surely is a very gratifying experience.
Cinnamon Bun: A Wholesome LitRPG - if you are looking for some lighthearted book to raise improve your mood, this is the one. It has good writing and really fun interpretation of an adventurous girl.
From the System with Love: A Quick Transmigration Story - A very nice novel where the protagonist is on top of things trying to get the desired outcome to save the timeline and earn herself a few benefits along the way. Again has pretty good writing.
Second Chances - A man gets a chance to relive his life when he goes and expresses his grievances at a bar. The only issue is whether he gets to keep his new life? Does he even want to, considering he is now a girl? He has to complete a mission to keep his new life. Will he give up the mission and go back to his old life despite knowing it could harm someone or will he choose to complete it and stay? Do I need to mention that this too has good writing.....
Some other great stories
Mouikkai Musume ,
I Didn’t Even Want to Live, But God Forced Me to Reincarnate! ,
Lolified ~ Restarting Back to Ten Years Old ,
Upside Down and
Azarinth Healer.
I'll stay away from recommending fanfictions because usually they depend upon how much you like the original work if you have even read or seen it.