What multiclasses would be a good idea with my GOOlock with weird stats

[Consensus]

I would like to multiclass a character I made with very little idea of mechanics, for my first real campaign. It is currently a level three great old one tomelock, although I could still change the cantrips I get from the tome as we have not yet had a session.
Shape Water (for getting find familiar from the tome invocation later so I can carry my octopus around)
Vicious Mockery
Friends
These are the three I got, I'm not looking for combat effectiveness, I mostly want a fun build that fits with the theme of being a cultist/illusionist.
My stats are sub optimal and have lots of odds in them. I was a half elf.
STR 8
DEX 11
CON 15
INT 13
WIS 12
CHA 17
I'm not sure if we're going to high levels or not, because we're using the mines of phandelver but I get the impression once with finish up in it we'd go to another campaign with the same characters.

[Sans.]

I would like to multiclass a character I made with very little idea of mechanics, for my first real campaign. It is currently a level three great old one tomelock, although I could still change the cantrips I get from the tome as we have not yet had a session.
Shape Water (for getting find familiar from the tome invocation later so I can carry my octopus around)
Vicious Mockery
Friends
These are the three I got, I'm not looking for combat effectiveness, I mostly want a fun build that fits with the theme of being a cultist/illusionist.
My stats are sub optimal and have lots of odds in them. I was a half elf.
STR 8
DEX 11
CON 15
INT 13
WIS 12
CHA 17
I'm not sure if we're going to high levels or not, because we're using the mines of phandelver but I get the impression once with finish up in it we'd go to another campaign with the same characters.

Honestly? For a casting Warlock, there's Sorcerer 3 and that's about it.

[Captain Morgan]

Why do you want to multiclass at all? Taking another level in Warlock gets you your first ASI which you can use on two stats with that spread, so you don't want to delay that. Getting hex + Agonizing Blast means you'll at least be solid in combat all the time. Warlock is a great class for a tricky illusionist as you start to get more invocations like Mask of Many Faces and Misty Visions, and higher level spells.

You don't have the stats for any sort of armor based class. I think if you were set on Multiclassing you should probably go sorcerer. A dip into dragon (or stone if it's allowed) will net you an increase to your pitiful AC. 3 levels will get you subtle and quicken spell. The former will let you cast spells without anyone realizing it which is clutch. The latter offers a lot of combat potential to an Eldritch Blaster.

[Consensus]

Honestly? For a casting Warlock, there's Sorcerer 3 and that's about it.

Yeah, that's what I thought, subtle metamagic would probably greatly benefit me.

[Consensus]

Okay now I want to ask how would my caster progression work, being both a spellcasting class and a pact magic class

[NecroDancer]

One level of bard never hurts a warlock. You get access of healing magic (not the best but still nice in a pinch), some great low level spells, an extra skill, and inspiration (d6s though but equal to your charisma modifier).