Dwarven Tomelock Build?

[LankyOgre]

Good day y'all,
I am playing in a 5E campaign that will be restarting in the near future and I'm in need of some advice. I played a Dwarven Tomelock up to level 5 and I'm not sure if I should continue or not. The DM is allowing us to roll new characters or continue with the previous ones. The party consisted of a barbarian/bard, a fighter, a ranger, and a paladin; therefore I went Warlock with the Outlaw background to fill as much of the missing roles as possible. I'm thinking that if I stay warlock, I will talk to the GM about switching a few things.
I never got into RPing the fiendish patron and it just felt flat. I'm thinking that I might ask to switch to the Seeker instead. We rolled for stats and I originally had Str 11, Dex 14, Con 15, Int 11, Wis 9, Cha 15 as a hill dwarf. I really like the idea of having access to all ritual spells through the Tome and I have enjoyed to walking artillery of eldritch blast. Does anybody have any suggestions for a 3rd invocation and reliable spells? I've searched for some Warlock guides, but they seem to be a little hit and miss if they include newer options.

If, on the other hand, you think the party desperately needs something else, suggest that too. The barbarian/bard may be rerolling a druid, and the paladin turned into a cleric for a bit, but may be going back. I'm pretty sure the ranger and fighter and remaining the same.

[Aett_Thorn]

Well, the party could definitely use an Arcane caster, and since it also doesn't have much of a combat healer (unless the Paladin does this), I would say that trying out a Celestial patron might work out well (from Xanathar's Guide). This will give you some extra healing options going forward as well.

The Ritual Invocation will be huge for your party, since they are missing a Wizard, Druid, or Cleric who could use them. This will give you huge utility within the party, especially if your DM gives you new ritual spells every once in a while.

Agonizing Blase should be a given, since it increases your at-will damage.

After that, taking a few invocations that allow you to cast some spells without using spell slots could help, so things like Misty Visions, Mask of Many Faces, or Armor of Shadows would be decent investments, as would Gift of the Depths from Xanathar's.

[LankyOgre]

Well, the party could definitely use an Arcane caster, and since it also doesn't have much of a combat healer (unless the Paladin does this), I would say that trying out a Celestial patron might work out well (from Xanathar's Guide). This will give you some extra healing options going forward as well.

The Ritual Invocation will be huge for your party, since they are missing a Wizard, Druid, or Cleric who could use them. This will give you huge utility within the party, especially if your DM gives you new ritual spells every once in a while.

Agonizing Blase should be a given, since it increases your at-will damage.

After that, taking a few invocations that allow you to cast some spells without using spell slots could help, so things like Misty Visions, Mask of Many Faces, or Armor of Shadows would be decent investments, as would Gift of the Depths from Xanathar's.

I took agonizing blast and I will look at the celestial patron. Any suggestions for spells? I’m wearing medium armor, so I don’t need Mage armor, but I will look at some of the newer at will spells. I completely misread warlock the first time around and wasn’t regaining spell slots on a short rest, so I’m sure I’ll feel spoiled for spells no matter what I do.
Thanks for the advice.

[Arkhios]

I'll second Celestial Patron for dwarf.
Traditionally Dwarves in D&D have been pretty devout and religious, so seeking a Celestial to be his/her patron is quite reasonable for a dwarf.