flatsninja, for a young lad just starting with tying you're doing quite well. Your crabs look good, but as you've learned, how they perform is important, and real crabs don't turn upside down. Since you have limited resources, IMO, it would be wise to concentrate on how things act & move & less on the actual form. A well known Florida guide once told me that it's more important that the flies for crabs & other flats creatures we imitate to move realistically rather than look real, as they're most often buried in sand, mud or grass while attempting to hide from predators that are detecting them via their movements. The predators usually only see parts of the real things as they attempt to flee.
If you look at patterns such as merkins (yarn crabs), Gotcha's or Crazy Charlies, and many other popular patterns, they all have basic shapes of crabs or shrimp, and materials that move well, some, such as rabbit hair, rubber legs, marabou or ostrich herl will move even when the fly is at rest.
In the past, I attempted to mimic various prey with great detail, but learned that simple patterns that moved realistically far out fished the detailed patterns.
Take some time when you can to observe the various prey species you wish to imitate & pay particular attention to their movements, even when they're sitting motionless, as you may still see subtle movement. Observe them when they're traveling normally & when they're fleeing. These are the features that you should be including in effective patterns with materials that mimic such motions.
There's nothing wrong with what you're doing, keep creating & tying, as that's the best way to learn. Just keep in mind that how the fly moves is most often more important than it's actual form.