Quite simple, it's just like the OG Bloodthirsty medal in the Call of Duty games. Even if you're not that good, you can try multiple different tactics, such as using sniper and marksman rifles and watching the objectives.
The way I got it, however, was to use the M249 LMG, as it's recoil is basically nonexistent, and the Phantoms faction, with the Blitz Shield. Stay in the back rank of your team and fall back into cover if you start getting hit, if you can safely get off a flank, you can either use the M249 or the shield to semi-safely bash enemies which will count for the killstreak. You can also chuck a grenade and possibly get a kill or 2 to start off each new life.
Good luck!