Taking in my clothes has saved me loads of shopping. You don't need to be ultra skilled.. running a seam down the seams of trousers or a top can be sufficient. Pin it first, then try it on carefully and adjust it where needed, then either tack it or sew it. It'd only take minutes if you know someone with a sewing machine, but otherwise, you could hand sew it using a small, tightish running stitch or backstitch.

Another thing you could try is add a section from one pair of jeans into the waistband of a second pair of jeans which fits you in the leg/behind but is too wide at the waist. You won't get this on Youtube - you'd just have to wing it. Slice out a section of waistband with the zip in the middle (before cutting the waistband, measure how many extra inches you need, then add on four inches for seams and adjustment). When cutting the rest, leave plenty of space around the zip to allow for seams. (you can always trim it back later). Cut it too large initially, pin it in place, then try it on and adjust it until it sits well. Turn in seams if you want to, and tack it in place, then try it on to ensure it's still sitting well. Once you have it good, you could maybe ask someone to sew it for you on a sewing machine. Ask friends for throw-away jeans to practise on.

Good luck.