Gear for pve and wvw?
Look at what you play the most.
If it’s wvw, make Ascended Celestial and use Exotic Assassin’s for PvE
If it’s PvE, make Ascended Assassin’s and Exotic Celestial for WvW.
Really try not to use same set for both Game Modes.
remember that it takes atleast 30 days (assuming you don’t have charged quartz crystals yet) to make celestial exotic or ascended armor. I personally think it is a waste to make exotic celestial armor is you intent to make ascended celestial armor in a later stadium.
As acotje said, look to what you play the most, and what gear you have now. for example if you have exotic berserker / assassins armor you’d better go for ascended celestial and keep the exotic berserker / assassins armor. Personally the difference between exotic and ascended ain’t that much.
dont get ascended armor for pve unless you plan on going hardcore into fractals, and dont make it until youre pretty high level. stick to exotic for dungeons/mapping.
if you plan to roam in wvw, ascended armor goes a long way cuz of wvw infusions. if youre gonna stick to zergs, dont bother and stay exotic.
head here to discuss wvw without fear of infractions