That is good. Coppersky’s compendium and Mai’s Loots and Stats are in the “UserGuide” here.
And, for the original question, the answer is the price is fair. The Damascus Blade is a rare mat, and the price for the gems alone is at the best rate available in the gem-store.
There will be offers better suited for beginners in the eggs yet to drop. Also, before events which happen about the second Friday every month there is an offer (5 actually) of 200 gems for 99 cents.
Every new player should take that offer. It allows three single pulls at the epic or elemental summons gate which mrans three heroes not less than 3*. Never feed 2* heroes, they are to be fed to these 3* cards you just drew.