Ender series is a good tinkering/starting kit with a big community. It’s a good way to get your toe in the water and see if it’s something you’ll like.
Cura is the standard slicer you’ll find most use, otherwise Simplify3D is good but expensive and PrusaSlicer 2.2 is great.
I’d recommend getting decent filament as the secret to 3D printing that nobody tells you going in is that it’s a whole lot of testing, tweaking, and trial and error to get all the parameters set. Each printer is unique and getting the exact speeds, accelerations, retractions, temps, etc is a real chore that gets easier but never goes away fully.
I’ve worked my way through probably 15 different printers over the past 2 years ranging from the low end to the high end. My favorite and current mix is an Ultimaker 3 with quick change, ruby tipped nozzles that will print anything from PLA to TPU, CPE, Nylon, etc and a Prusa Mini that is more for general use things when my kids want me to make them something (PLA or PETG). Start with PLA as it’s safe and the easiest to print with as a newbie.
Thingiverse.com and the new Prusaprinters.org are the best free stl sites. Thingiverse has been around for ever and has endless models, but it flakes out a lot. Prusaprinters is run by the famous Prusa brand and is growing really fast.