I'm going to assume that you're a beginner, so forgive me if some of this sounds condecending
IMO, here is the checklist order to go through.
1) Driver technique
- If the understeer happens under acceleration, be gentler on the gas, only really put the hammer down when the front wheels are straightened out. It's FWD.
- If the understeer happens on corner entry, you're going too fast in and/or you're not blending the braking and turn in well to get weight transfer to the front tires to get more grip there.
- Change your driving line to cover up the understeer/FWD. Not sure on this one, not a FWD guy.
2) Tire pressure
- Each tire/suspension will have an optimum air pressure to get maximum grip. You have to figure that out yourself. Set tire pressure so there is maximum grip in front and then put a non-optimum pressure in the rear. You can get less grip by making the pressure less than optimum (to make the sidewalls bend, making a bad tire patch) or making the pressure more than optimum (to ballon the tire, shrinking the tire patch).
- A good alignment is a good idea in general. As long as you don't go really radical, in general more negative camber gives more lateral grip, but you give up a little braking/accelerating grip. Toe also has a minor effect, but it's probably not worth youre time.
4) Stiffer rear swaybar/softer front swaybar
- The stiffer side transfers weight faster on that end which reduces grip there. This is the cheapest/easiest car mod do to tune static under/oversteer.
- Stiffer swaybar also reduces car roll, which can sometimes give more grip (which is opposite to what you would expect) if the reduction in car roll optimizes the the camber setting for the tire. This is typically not the case though.
5) Stiffer rear springs/softer front springs
- Same mechanism as the swaybars. Requires more work in the mod and also reduces ride quality more than the swaybars. Go too crazy with the change in spring rate, you'll also want retuned shocks.
6) Adjustable shocks
- This effects dynamic over/understeer when there is weight transfer happening. Not going to try to explain this as its complicated and you're probably not going to go this far if price is an issue.
7) Wider front tires/thinner rear tire - don't do this on a daily driver
8) Shift weight bias to the rear - don't do this on a daily driver