Im at the 3month mark of starting as a complete beginner. So far, i can play
- hot cross bun
- row row row your boat
- twinkle twinkle little star
- snow by RHCP (99% of my time was spent on this one)

classic Snow one still cant play it after years of playing guitar to be fair i didnt really try to learn it
but cool and simple riffs to get into it should be:
Nothing else matters
summer of 69
Smells like teen spirit
and if you can do all of this just go for Canon Rock