Too much excess yarn

I just started knitting, I used a double cast on, and then started to knit, but after a short time, a large excess of yarn shows up between the needles (two pieces) I’m thinking it’s because I’m knitting tighter than I cast on? Is that right? or how do I fix this?

On an unrelated note, which cast-on method would provide as stiff an edge as the basic knit bind-off?

Just keep working - nearly ever cast-on will have some slack. Slack is a good thing; you don’t want a super-tight cast on edge, or your finished garment won’t stretch at the bottom. (Ditto for cast-off edges)

Well, this is more than just a little slack. The needles get to be 1 - 2 inches apart and the stitches are only about 1/8 - 1/4 inch wide.

And I’m not knitting garments which is why I want the edges to be as ridged as possible.

Just keep practicing. It takes a while to get really good at knitting - get used to how to make the stitches first, then work on getting an even tension. It’s best to start with some practice pieces first, rather than just start in with whatever it is you want to make and be disappointed that it’s not turning out like the pictures.