My first couple of flights were short easy ones I knew I could do. Returning to my home airfield.
I have gradually built on them since, now up to 80 hours total in just less than a year and a night qualification on top.
Just go and build your confidence a bit then take some longer trips. You will continue to make mistakes, just learn from them.
As regards other aircraft, i have only just recently been checked out on a C150 after nearly 70 hours in a PA28. Its up to you really but I would suggest getting fairly confident in the one yo have spent time in first.