Since low budget is stated as a main requirement, I am assuming that professional repainting is not an option. Hard to tell from a photo, but the scratch on the side probably will not buff out. But I would try anyways to be sure. A good random orbital buffer with a medium cutting pad to see if it buffs out, then polish it back to a shine. If that works, great, if not, need to repaint. The leading edge of the scratch on the passenger front door might be able to buff out, so you don't have 2 panels that need resprayed.
The peeling paint on the fender will need to be painted. You can get OK results painting a fender with a rattle can if you use a high quality product like what you find at APS Tower Paint company. Get your paint code and order a couple cans per panel, a couple cans primer, and a couple cans of clear. Remove the fenders if you can, and if not mask the surrounding panels off with tape and also plastic sheets so you don't get overspray on the other panels. Prep the panel by sanding with 80 grit, then 120, then 200. The instructions on the primer can will say what grit you stop at, which is usually 200 or 320. Don't use finer sand than what the primer can says because primer doesn't stick to a surface that is too smooth. Wash all the sand off, and let it dry, then prime. Now look at the instructions on the color coat, and after the primer is dry and ready to be sanded (as per its instructions), do so. The color coat will probably say you need to wet sand the primer with 400 grit. Again, don't go any finer or the color coat won't bond properly. Wash, dry, then pain with the color coat. Once dry, as per its instructions, next wet sand the color coat according to its instructions. If it says don't wet sand at all, then don't. Do whatever the paint instructions say, then wash, dry, and apply the clear coat. You will end up wet sanding the clear coat with 1000 or 1500 grit, then 2000, then polishing to get the shine.
Fenders will turn out OK with cans, but the door panels may not turn out so well. Painting a wide area needs a wider spray pattern than any can can do. The result might be that you might be able to see the overlap if you look hard enough at the finished product. However, that will still look better than a scratch, and also prevent that scratch from rusting out the panel.
Please understand that the colors of the newly painted panels may not match the surrounding (not repainted) panels 100% because they may have faded over the years. If you look closely, from a distance, you might see a difference. Body shops will blend into the surrounding panels so this is not noticeable.
You will want to polish the entire car, using a medium cutting pad on the panels that weren't repainted, and polish to get those panels as smooth as the ones you repainted and wet sanded, and this also might help getting the colors to match because the old panels might be slightly yellowed due to UV over the years, and a medium cutting pad will remove that.
I see in the pictures there is some orange peel in the existing paint (because the outline of your legs reflection is jagged and not smooth), so you won't want to wet sand and polish the newly painted panels/areas to a smoother consistency than the other panels. Or, you can wet sand the existing panels as well, and that car will shine like it never has. But that is a lot of time consuming work.
For that small area of missing paint on the drivers rear door, I'd be tempted to only do those area and blend into the rest of that door panel and rear fender. It won't be perfect, but painting the whole door panel with a rattle can runs a higher risk of ending up looking worse.
The cost of paint and materials will be about $200 to $300, and it will take several hours of your time. Be patient and follow the directions on the paints to the T.
I'd stay away from the paints sold in auto retail stores or touch-up bottles.