As @Fleg suggests, a Tier II purchase the next time Amanithrax comes around will help you get the pet to Level 10 if you complete Pure Faction 100.
Pure Faction 200 isn’t worth doing in my opinion, as you would need to complete 300 to have enough pets to get to Level 15.
Have you checked out: Pure Faction Breakdowns - A Level 500 Faction Guide
I haven’t, but the presentation was done way better than my half-assed: Delve Faction Team Strategies
So I’d recommend the first link first, mine second. Both have links to the super duper mega mega thread. gl hf