I am a level 51 and i am doing winter tusk before i start celestia and i personally feel that wintertusk is a little tuff but gives you huge amount of xp. I have only done one boss battle and couldnt beat it without help idk if its my armor or my level.Should I continue wintertusk and power through it or leave it and do celestia and come backto it?
In my opinion, Celestia is generally the same experience as Wintertusk, from a difficulty standpoint. If your gear has Critical Hit/Block it will benefit you tremendously. In the levels of 50-58, your gear will potentially change ever two levels, so make sure to increase your gold with trash gear sales, and check with the Bazaar often, as well glance at the Vendors in both Celestia and Wintertusk for gear options.
Please remember that there are Astral spell trainers in Celestia as well that offer spells which may benefit you. They are located at the Celestia Base Camp.
If you have a "Friend" list containing wizards who are around the same progression as you, I encourage you to seek them out. If you have the patience to repeat content so they can progress along side you, that will only benefit you both in the long run.
I believe at level 55 & 58 you may receive announcements from the major NPCs to come visit them offering quests, rewarding you with spells/pets to assist you even further in your progression.
Remember to keep your gear up to par with the current content, as best you can. Attempt to train a "beneficial" pet to further assist you. If you mostly play solo, like I do, try not to place spells in your deck for every situation, just what is absolutely necessary to avoid excessive passing and discarding.
I hope these general tips help you in your progression through Wintertusk, Celestia and beyond.