You have a lot to go man. My main accs has reached rank 3, I have a fully maxed dual spartan r5 alt, and I co-pilot ialdo SM. What I've learned for making builds as a noob, if you can't get anything good make dual malice beam. I got rank 1 with them on an old account of mine that I sold. Add EMP or OEMP if you have one. You don't need premium mods, I did it in all E-M mods. For a physical build, don't get too ahead of yourself. Spartans are hard to get, make a nightfall build with night eagle and rock recoiler.
Please do not waste your time on grim reaper, its one of the worst torsos in the game. Follow my advice for success, trust me.