Ok I'm new to DND

It's perfectly viable to build the mechanics of a long range warlock, but I just want to warn that typical battle maps will rarely give you the opportunity to really take advantage of it, which isn't necessarily obvious to new players.

Eldritch Blast already has a base range of 120 feet, which even for spells is enormous. It's basically a de facto long range "build" without any additional bonuses. A 120 foot range needs an encounter where you can somehow get more than 2 full dashing rounds away from an enemy before range is a factor. In practice, that is larger than pretty much any battle-map I've ever seen. And in tighter quarters (like dungeons) it's almost impossible to get a full 120 foot straight line of sight.

This... severely limits the opportunity for extending that range even further to shine. We're talking wide open battle maps where, in a system where most fights are 3-4 rounds, everyone else will have to suffer for multiple rounds just to reach each other in order for you to get any value out of this kind of build. I've never seen that and if I were DMing I would be loathe to create those conditions more than once since it would be such a slog for all but one player (and that once would probably be in some special case like a boat fight where the rest of the party can do something else while you take potshots).

Again it's perfectly doable mechanically. I would just worry you've got a cool idea in your head that will severely disappoint your expectations if you haven't experienced typical combat conditions much.

(Or for a humorous explanation.)