Please rank the following puzzles in order of difficulty

I signed up for my first WCA event and i only can solve the 3x3 so far.

I wanted to learn another puzzle for the event because i have 3 weeks left.

Please help me find some "easy to learn" puzzles, taking into account the number of new algs i have to learn and the understanding of the puzzle.

I don't aim for specific times since even for the 3x3 i average ~50s.

The puzzles are the following:

1. 2x2

2. 4x4

3. 5x5

4: Pyraminx

5. Megaminx

6. Clock

Thank you <3