I'm assuming that you have the appropriate ruler platform to use templates safely.
Gadget girls:
https://www.thegadgetgirls.com/
And HandiQuilter:
https://www.handiquilter.com/shop/category/rulers/
I started off with a set of circles, and ovals. You can really do a lot with those 2 shapes.
My personal favorite is DeLoa Jones:
http://www.deloasquiltshop.com/shop/guides.html
Her circle busting templates allow you to quilt without being a contortionist, and her boomerangs are easy to use for curved crosshatching.