I think using mostly recycled fabrics is a great way to get started. It doesn't cost much and you can get plenty of practice and not be disappointed when you totally screw up a diaper.
Once you have it down and are feeling confident, you can move on to more expensive fabrics if you want. But you really can just do all recycled fabrics and still have a wonderful stash. The t-shirt diapers I made are our favorite fitteds.
Overall, as long as you don't go overboard, then yes, you will save money.
Here's a run-down for how much I spend to make different diapers:
pockets (no insert): $3....pul and suedecloth
AIO: $5-6....pul and hemp or birdseye
hemp fitteds: $5-6....cute outer print and many, many layers of hemp jersey
recycled fitteds: $.50...free fabric, only costs are thread, elastic, and aplix
recycled AIO's: $1.50...$1 for pul, free inner fabric
covers from fleece jackets: $.50
cover from pul with foe: $2.75
Those prices are for aplix diapers. Anything with snaps is about $.50-.75 extra. And these prices are for large diapers. Newborns and smalls would be quite a bit cheaper.
All of it is cheaper than what you would pay for new. You just have to decide how much your time is worth. If it will be just about as cheap just to buy a bunch of prefolds and you don't really have the time to sew, then just go with prefolds if that works for you.
And don't worry about not knowing much about sewing. You'll catch on quick. I started where you are. Threading the machine and sewing a straight line.
I just practiced and went for it. The first diaper wasn't even functional as a diaper. But I got better. The third and fourth diapers I made are still in my stash. I use them as night time diapers and they've held up really well. Cosmetically imperfect but I'm the only one who sees them so who cares?