Here are you options mate:
Propecia, Tricomin, Minoxidil, Revivogen, Nizoral Shampoo, and countless others.
For you you should DEFINITELY get on either Minoxidil (Rogaine/Regaine (u.k.) or Tricomin. ASAP, like now. Seriously the longer you wait and dither the worse your sitatuion will become nad from those pictures your situation in terms of regrowing hair looks potentially great considering diffuse thinners respond better to treatments and yours is very consistent on the top of your scalp.
If you dont' want to use propecia for now, then ok fine, it's cutting your chances of getting some serious regrowth down by a lot, But note, that 0.2 mg of Finasteride (Propecia) was shown as almost as effective as 1mg - so that's definitely an option espeically considering your're young. And it would mean you have far less finasteride running around your system potentially causing side effects (which by the way are in a far minority)... also it makes the cost cheaper. getting the finasteride and a pill cutter, cutting them into fifths.. lasts 5 times as long for the same price eh?
google tricomin and Copper peptides. You'll probably find some vague bs about it but there are real studies that have shown them to be just as if not more effective as Minoxidil, without the side effects, and Tricomin is cosmetically amazing in that it makes your hair look better as well. Minoxidil will make your hair look greasy when you use it.
I'd recommend if you did ANYTHING right now you get minoxidil and trico. They can work together to pull off some amazing results.. seriously. i've seen them.
Be aware that hairloss in many cases gets worse before it gets better when using treatments. Because the miniturised hairs fall out and thicker hair shafts grow back, which again fall out and generally continue to get thicker until they're relatively stable and you have quasi normal hair growth again.
I'm not trying to say it's a timebomb.. you still have plenty of time. But if you just get on minoxidil and trico now you can work out the rest later.And the whole point si with hairloss treatments, the earlier you start the the higher your chances of maintaining/regrowing hair.
You're worried about side effects. So forget propecia for now. Just get on Rogaine/Nizoral/Tricomin Spray. Stay on it for at least 3 months.
Good luck and
Best wishes
Sam