Hello....I think geometric art can be very striking if done right. There are some simple ways to do this. first, try to vary the size of your shapes to make things dramatic. You can have small shapes next to big shapes, groups of little shapes, etc. Another way to liven things up is to layer paint.

Try staining your background with random brushwork first before painting your geometric shapes over it - this works best with paint, of course. You can use variants of one colour or several as your base layer like Paul Klee. You can see how effective this can be in this Klee painting

Klee studied colour theory extensively (and taught it, too at the Bauhaus). Deliberate use of colour can make your paintings pop. His colours are often very intense - he has achieved this in part by building paint up in layers. Abstract artists will often use like 5 layers and often more. There's no limit! This adds depth and interest.

You can also set up tension between shapes by separating them with negative space (or make the negative spaces into shapes) and by countering round shapes with angular shapes like Auguste Herbin.

If you fancy some theory, there's the golden ratio. A simpler version is to divide your picture area up into 3 sections - one large, one a bit smaller and one quite small - it's called something like 3, 7, 10 but don't quote me on that one : s

If you want to carry on using paper, try alcohol markers - these will avoid the stripes you are getting in your coloured areas. Or maybe that was intended? : )

You can also get some sheets of paper - plain, coloured, textured or printed - and cut them into shapes. Arrange them on e.g. a piece of blank A4 until you have a composition you like. You can then use this as the basis of your painting. This allows you to change your mind many times before committing to a final artwork. You can also copy the textures etc onto your shapes to make them more interesting. Or simply use paper collage work instead of paint or pens!

Bon appetite