Beat a friend's challenge 5 times.
For this you need to beat a friend's challenge under the Challenge menu. You will have to accept the challenge for it to count. Once you have beaten the Challenge given, go back to the Challenge menu and send the challenge back to your friend. Your friend will need to beat the challenge that was sent to them, and then they send it back to you. Each of you will need to do this 5 times and you have 24 hours to complete the first four, and the fifth on is 2 hours to complete. I would suggest deleting the friend's you have and only keep one, that you and him/her can just get each others challenges. Also if you get challenges like, exp. kill 2 enemies with melee, don't go around killing 20 enemies with melee. Just get 3 kills so its easier to complete.
Note: That the player to complete the 5th challenge (500xp reward) will be the only one getting the achievement. So make sure the player who is going for the achievement finishes the 5th challenge. Also beating your own personal best also counts towards ...I Can Do Better.
Boosting Method: Have just 8 friends on your list with the game. Create 2 different squads, with 4 people in each. Go into a Squad match and search Decoy (3 rounds, 10 minutes each = 30min game mode) together. If one squad gets an empty lobby, back out and search for that empty lobby. Once both squads are in the same lobby you can do the challenges & volleys much easier, since all 8 of you are on each others friends list. Doing the fire volleys will also count towards your ...I Can Do Better achievement. This method also works to boost any of the other online/squad achievements, not just the challenges.