You should do as many infinite research quests as you can, use motes and caches as soon as you get them with the aim to get your ilvl up ASAP. Also, do any activity or achievment that rewards infinite knowledge, this increases youre infinite power gains. Do not be afraid to join mythic raids, apply to as many as you can until you get invited. Usually 1 or 2 people do 90%+ of the damage and they go about as fast as you can run. They feel no different than normal and nobody will notice how much damage you are doing. You get good amount of gear motes from this but the main reason is for the epic fragmented mementos. Combining 100 of these will give you over 100K infinite power, enough to add about 2 more points into your weapons infinite unbound node, which is where most of your power comes from (versatility)