From what you describe, I think the 1st and 2nd pictures are more what you are aiming for, yes??
I would start by deciding ... do you want a straight set or on point?
Sashing?
You don't necessarily have to stick to one color palette, but perhaps a group of *like* colors ... for example, all primary colors, all pastels, etc.
Also, I personally like a "balanced" sampler quilt. So choose (for example) star blocks for corners and the center with other blocks filling in the balance.
Sometimes it helps to go shopping for fabric, find a focus fabric (something you will use in all of the blocks, not as a background, but part of the block), then choose other colors within that fabric in solids or tonals to balance it out, and a complimentary background and sashing if desired.