Keep Practicing!
You'll start getting much better as you go along with this. I want you to research how to do basic mixing and mastering online with FL Studio. Then apply those techniques and new founded skills to your next track release on Newgrounds. Your sound quality will improve dramatically as a result. Mixing/mastering is hard to grasp at first, but watch some YouTube video tutorials and study online guides for beginning mixing/mastering. You won't fully understand most concepts at first, but you need practice and study to get there.
Also, for getting some better bass sounds, I want you to Google "free vst bass" and check out the first result from freemusicsoftware.org There are some decent free software synthesizers on there, and if you need help installing them just send me a message and I'll help you out when I get a free moment.
Best wishes and keep practicing! Electronic music production in software is not only compositional practice - it's production and technical skill too... Music is very technical, so dive in and learn as much as you can!