If it’s like the Morrowind expansion, you should wait a bit. There were some pretty great all-in-one packages that came out around that time.
Edit:
Here - Product Details - The Elder Scrolls Online
Pre-purchase The Elder Scrolls Online: Summerset digitally to receive immediate access to the full base game and the Nightmare Senche Mount, plus get a bonus copy of the Morrowind® Chapter for a limited time. Also includes the Queen’s Bounty Pack pre-purchase content.
Or here - Product Details - The Elder Scrolls Online
The Elder Scrolls® Online Collection includes the ESO base game, ESO: Morrowind® Chapter, ESO: Summerset™ Chapter, and four DLC game packs.