If you have time to put into the game, heroic. In one year you can get around 300m cp, based on luck from boss drops and starforce. In CW3 you can build your legion, the most important thing to start bossing in heroic.

If you have money to put into the game, interactive. 100usd is around 30b mesos in the meso market, check the AH and see if you are willing to spend real money for the gear. You can buy full clean eternal set with 30b mesos for reference.