Is there a way to make a complex model easier to fold during the learning phase?
A couple of things that come to mind:


Don't try to run if you cannot walk yet. In other words: do some simple projects first. You obviously like the finished results of the more complex ones better. But by trying easier ones first, you gain experience on how to read the diagrams, and you're practising the techniques for precise folds. Plus: better a nicely finished 'easy' project and the feeling that you succeeded, than a complex ball of paper and you giving up completely, don't you think?
Larger paper makes things easier to see and to fold. I know dollar bills come in only one size, so you'll need to cut your own piece of paper. Make sure the proportions match.
If you insist on folding the complex item, try to figure out till which point you still understand the steps; you must absolutely be sure whether folds go up or down, or maybe between two parts of the paper. Your result may look similar, but if it's not completely the same, you'll find out sooner or later. So, check and double check and maybe ask someone else if they notice any differences.


Good luck, wishing you a lot of fish.