Quoted:
I want it as a multipurpose weapon home defense/range/tactical. I don't want to limit myself.
As the poste above stated there an absolute ton of pinned topics in the technical forums dealing specifically with this type of question.
That being said, your future "enhancements" will depend largely on your budget considering you want a "do all" type of rifle.
(In order of importance) you need to purchase:
Ammo
Magazines
Range time
Shoot the rifle for a bit and become familiar with how it operates, how you want it to "handle" (balance, weight, etc.), how to clean it properly, and basic disassembly procedures. (I'm not being condescending here, you need to know these things so you can perform the work yourself and make informed decisions not based on what the internet says).
A railed foreend will allow you to attach a flashlight, bipod, and maybe a vertical grip (I don't much care for them). Prices range from $50 to almost $400.
Things to consider when buying a new foreend:
*your budget
*Whether you care to free-float the barrel or not (relieves pressure on the barrel from your sling/bipod/etc. and prevents POI shifts)
*Weight (some rails are light––Daniel Defense, some are heavy––ARMS)
*Ease of installation (depends on manufacturer of foreend––2 part non-freefloating foreends are the easiest to install)
*Do you want/need rails the entire length of the foreend? some manufacturers make foreends that allow you to install sections of rail where you need them (JP Enterprises, PRI, et al)
Shooting the rifle extensively will help you figure out which changes you need to make to better fit your habits and stature.
You may decided you don't care for the standard pistol grip. Magpul, ERGO, TangoDown, and others make replacements. The prices range from std. A2 grip at $3 to others at $50.
Most people prefer a collapsible buttstock since adjustability allows it fit more shooters. The manufacturers are too numerous to name here but Magpul, VLTOR, LMT, and others make great stocks. VLTOR and LMT stocks (IMO) offer a better cheekweld than the others, but the Magpul CTR doesn't rattle and locks up solid. Shoot more and figure out what
you want.
You didn't say whether you had a flattop or an A2 config. (built in carry handle). I'll assume a flattop. If so, you'll need a rear sight. Do some reading; there are tons of manufacturers out there. I prefer PRI, Troy, and GG&G because they lock up solid and are well made. YHM and Midwest Industries make good sights at a lower price point.
About the only "generalized" advice I can give you regarding accessories is:
1) Shoot your rifle, determine what you want to change, and come here to read the various opinions concerning each particular piece of kit (make sure those opinions are based on use and not some knucklehead "parroting" what he's read elsewhere).
2)Don't put Airsoft Garbage on your real rifle. The stuff isn't made to spec, has spotty Quality Control at best, and is usually cast out of shitty potmetal. I've personally seen sight adjustment screws snap off, canted rear sights, and spotty windage adjustments. Do it right the first time.