Whilst good libraries can help your overall quality I feel the target for your efforts lies in the orchestration and song production.
The first song on soundcloud feels very loose in the timing between individual parts.
There are held chords which drown out the other parts in both the 1st and 2nd songs and cause clashes with the other parts.
Depth of dynamics in the individual parts or as a whole create that flat sound which takes away from emotional impact.
Your 3rd piece is stronger but still clashes sonically and had no movement in the dynamics but has more cohesiveness than the two earlier tracks
You don't need super high quality samples to get work but it can help with presentation.
Don't worry, I started out with similar issues but one of the things I learned was how to polish the hell out of whatever I wrote with whatever samples and libraries I had at my disposal. I think that is where you need to concentrate your efforts.
Concentrate on how to use frequencies of various instruments together and how to compliment the different parts together.
Learn to analyze your own music and other people's. You can learn a lot by analyzing their techniques to improve your mixing both in terms of instrument frequency, mix frequencies, support instruments, and over all production will help improve you to a point where you can listen to your music and say to yourself that it has a quality high enough for someone to pay for it.
Those are not realistic samples at all and while specifically targeted at game boy and ds market listen to how the instruments either work together or compliment or offset one another.
This is an example of the same type of low quality not realistic samples working together and produced differently (eq, reverb, compression) but together everything feels cohesive. If you can produce good tracks with the tools you have then it makes it easier to produce good tracks with more advanced tools.