Here’s a side desk I’m currently building.
I used a birch top from ikea which I cut down to size. The rest is just construction pine from Lowe’s which I planed and squared.
No screws or nails. I used a chisel and hammer to cut out openings in the legs to put the cross boards in. It’s super sturdy as is and I plan to add a slanted shelf to the top.
My other desk I used Baltic birch plywood and a birch top again.
If you want something that’s going to last use some hardwood or even softwood like pine.