Help optimize a Linguist Build

[Blas_de_Lezo]

Concept: a linguist that uses his vast knowledge of languages in his advance. This means language dependant spells (such as charms and dominates) and assuming other humanoid forms to impersonate other races.

Class: Warlock Great Old One 1? (to communicate mentally with Awakened mind) / Bard 5 (is there any better combination?)
Level: 6
Race half-elf or changeling, possible the last one (3 total languages)
Background: Sage (2 languages)

Feat: Lingüist (3 languages)
I don't know what are the most useful languages (possible the most common ones and the ones for peoples that don't know common?): Giant, Primordial, Draconic, Deep Speech, Undercommon, Orc, Goblin, Infernal?

Signature spells:
Cantrips: message, friends, vicious mockery
Level 1: Charm Person, Comprehend Languages, Disguise Self, Dissonant Whispers, Healing Word, Speak with Animals
Level 2: Magic Mouth, Suggestion, Alter Self, Invisibility
Level 3: Tongues, Sending, Speak with Dead, Speak with Plants

[xyianth]

Disclaimer: These are just general ideas for inclusion in your build at some point, not necessarily recommendations for an optimized build.

As far as a linguist goes, there are a few abilities that seem important to include:

Druidic from druid level 1
Thieves' Cant from rogue level 1
Awakened Mind from great old one warlock level 1
Eyes of the Runekeeper invocation
spells: vicious mockery, command, suggestion, dissonant whispers, speak with animals, speak with plants, speak with dead
The monk ability Tongue of Sun and Moon would also be useful, but it requires a significant investment into monk for an ability that can be replaced by language proficiencies.

The above features can be included with minimal investment by adding a 1 level dip of druid, a 1 level dip of rogue, and a 2 level dip of warlock to a bard build. The Linguist, Actor, and Inspiring Leader feats are also nice thematic additions.

[Maxilian]

I would say go to Warlock 2, so you can get invocations, there are 2 invocations that work for the build:

Eyes of the Rune Keeper: Let you read all writing
Beast Speech: You can cast Speak with animals at will

If one or the other its not of your interest, you can get the improvement to Eldritch Blast (to make sure you will always have your own things -Will make sure you don't become "weaker" with time)

You could push to lvl 3 Warlock so you can get a Familiar, the specials familiars have their own languages (Imp have Infernal, Pseudodragon have Draconic, Quassits have abissal and Sprites have Elvish and Sylvan) -So for languages, Sprites are more useful cause they know 2 unique languages -something that is not common--

Note: When it comes to races, most races give 2 languages, common and the one of their races, but there are some that give you an extra one like High Elves (Common, Elvish and an extra language -The also give you a cantrip, so for the theme, you could take "Message")

Forest Gnomes, have 2 languages only (Common and Gnomish) but they got the ability to speak with small Beasts

Half-Elf, have 3 languages (Common, Elvish and an extra of your choice)

Firbolgs (From Volo's Guide to Monsters), have 3 languages (Common, Giant and Elvish), they also got the ability to communicate in a limited manner with beasts and plants

Yuan-ti (From Volo's Guide to Monsters), have 3 languages (Common, Abyssal and Draconic) and Animal Friendship -but only with snakes-

Arakokra (From Elemental Evil player's companion), have 3 languages (Common, Arakokra and Auran)

Deep Gnomes (From Elemental Evil player's companion), have 3 languages (Common, Undercommon, Gnomish)

[Fishyninja]

Feat: Lingüist (3 languages)
I don't know what are the most useful languages (possible the most common ones and the ones for peoples that don't know common?): Giant, Primordial, Draconic, Deep Speech, Undercommon, Orc, Goblin, Infernal?
A very interesting concept, which I like a lot.

In regards to which are the most common languages....be careful here as it can be very DM dependant depending on what they fill their world with.

In my Opinion if you can speak:

Common
Elvish
Dwarvish
Goblin

You should get by for a quite a while. Again as xyianth mentions don't forget code/sign languages like Thieves Cant.

[Blas_de_Lezo]

A very interesting concept, which I like a lot.

In regards to which are the most common languages....be careful here as it can be very DM dependant depending on what they fill their world with.

In my Opinion if you can speak:

Common
Elvish
Dwarvish
Goblin

You should get by for a quite a while. Again as xyianth mentions don't forget code/sign languages like Thieves Cant.

That's nice, but Elves and Dwarves speak common too. What about races that only speak their languages?

For example, some giants and trolls only speak Giant.
Elementals only speak Primordial.

Is there more "common" monsters who only speak one language?

[Fishyninja]

That's nice, but Elves and Dwarves speak common too. What about races that only speak their languages?

For example, some giants and trolls only speak Giant.
Elementals only speak Primordial.

Is there more "common" monsters who only speak one language?
I have to admit I honestly don't know I only mentioned those as I am AFB and it seems they were the most common (in my mind).

[Farecry]

Knowledge cleric 1 gets you some more too.