You can complete these challenges on Normal difficulty and still gain the rewards so if you don’t want much of a challenge, turn down the difficulty. If you do, consider fighting Elites as well.
Once again, Blasteroid is a good map as you can avoid the Ravagers’ line of fire more easily and can move round the map with ease. If you have access to Cryo or Incendiary ammo, use it now. Biotic users can freely spam powers and combos as Reapers are incredibly vulnerable to them.
As this is a solo challenge, it brings a certain level of difficulty but if you are a decent level and have good equipment, you should be able to keep them at bay. Soloing requires a lot more run and gun tactics, never staying in one place for too long.
Take the opportunity to get the high ground whenever you can to make things simpler for you. The back, right corner allows an excellent view of the spawn points though it is also a spawn point so keep that in mind.
At the start of each round, look for which spawn point they will come from and move accordingly. Try not to get stuck on the lower ground too much as enemies will come from both sides and can shoot you from above. Ravagers are exceptionally good at that. As a reward for completing the match, you will get 5000 Credits.