Build it yourself. I'm not sure where you are on the world but if you live in the UK there are some really good custom PC / Laptop manufacturers out there - I'm not going to drop any names because I don't want to appear like a representative of that particular company but searching 'custom built PCs / laptops' or something to that effect in Google will give you the best companies at the top of the first page. It's bound to be the same if you're in continental Europe, Australasia, North America or Japan.
And some adivce - pay big or don't pay at all. In the past I've brought computers people insisted were 'great value for money' and 'amazing midrange,' etc. Don't listen to them. I've estimated in the UK you have to spend at least £700 (not sure what this is in USD) or more to get a computer that is:
1) Going to last at least two years without showing any signs of age
2) Not going to require any expensive upgrades (upgrading really burns into the wallet over time) for several years
3) Can run all games on the market at top, or near top graphics really, really smoothly.
Finally, get a laptop cooling pad. If mobility is essential (I'd otherwise advice getting a desktop for gaming) then you'll need this to keep your computer cool whilst gaming, because your computer getting hot greatly decreases its lifespan.
I'm afraid nobody knows ESO's specs at the moment, but I imagine them to be fairly high. Besides, you won't want to spend so much money for one game alone. Look at other games you like / want and see their specs as well, and keep that in mind when purchasing.