The sky has no limit when modding AR15. It has infinity configurations or looks when comes to it. It all depends on your needs and budget.
Stop by and BROWSE this forum AR15 pics thread. There are tons of configuration pics or looks which you will get your attention on. From there you will get an idea which route to start with..
Speaking of light, i love Inforce WML with the HSP/IWC thorntail offset mount.
And i also own both Streamlight TLR1 and the TLR1 HL. They are just like the famous Surefire X300 but cheaper. To me the Streamlight does the job enough and quite happy already. You can always get them from Amazon.
Not sure which grip you meant, but let me go through about pistol, vertical and angle grips.
For pistol grip, i love BCM Mod 1 or the Magpul MIAD. The difference is BCM's is more vertical compared to the MIAD.
Lots of Vertical and Angle grips out there. Also check out "Hand Stop Kit" From the simplest looks to the fancy design. From the cheap Magpul BUT works to the more expensive models made by others.
I eventually swapped all Magpul Vertical Grips to Magpul XTM Hand Stop Kits.
Let's put this way, check out the following sites below. You will see what brands they carry. So that way you will be able to justify which models you like, price ranges or maybe reviews.
And finally here are the old pics of my builds. Some of them had changed configurations.