Here are some tips that can help you wallet and AC do better.

1- Don't be stingy. You can sell parts back for as high as you bought them, even if used.
2- The best stuff doesn't always cost the most! The cheapest heavy leg type is better than the most expensive in most aspects.
3- The best weapons and parts don't come til a new stock, or some arena advancements, so don't use the AI until they've arrived.

These can really help any new AC3SL player.