How to make speakers perform better as cheap as possible?

Rings: https://goo.gl/Hq6trW
Sound Proofing: https://goo.gl/ghqc3N
You don't need to spend thousands on speakers to make them sound amazing. The first two steps that don't need to break the bank for getting speakers to work better is ensuring you have the environment correct. Sound deadening and speaker seals ensure you get your sound into your cabin and the speaker works correctly.

1. Ensure you sound deadening your vehicle. This is the most important part. Speakers do not work 100% without the correct enclosure and this stops outside noise interfering.

2. Seal your speakers against door trim. This again allows the speaker to work correctly and also ensure you don't lose Soundwave's into the door cavities.