Amazon is selling this set of SunFounder Arduino starter kits for around $20. They seem to have everything and get good reviews… seems like a good way to get started.
Link: https://www.amazon.com/dp/B07F9NB7SB
Coupon Code: ANL64QCS
Price for the Uno Rev3 version is $19.79, or $20.99 for the Mega 2560 version.
Happy tinkering!