1) Pointy ones
, comes in 30mm x 9mm
= Use 3/8 ribbons
2) Square ones
..comes in 40mm (not sure if it comes in 30mm) = Am assuming you'll hv to use the 5/8 ribbons. I know the 50mm, one uses the 5/8.
Alligator Clips = Single Prong and Double Prongs =>> 3/8 ribbons.
and welcome to the Forum...
Edited to add: Which ever you choose, pointy or square, it's a matter of YOUR personal preference... =)