How long it is since you last played?
I'd suggest starting with a single month sub, that gives you access to Morrowind, Summerset and all the DLCs (in other words, everything besides Elsweyr) to see how much the game changed and if you still like it.
I believe if you buy Elsweyr before June 4th it will actually give you Morrowind and Summerset content as well, then it would only be specifically DLC which you would need.
That would either come from ESO Plus and monthly payments for access or via individual purchases from the Crown Store.
his_emailb16_ESO wrote: »LIterally launch, first few months. I'm particularly interested in the Necromancer, tho