Your opinion on Multi-classing for my Level 4 Battle Master

[Slybluedemon]

Hello Guys and Gals, This is my first time posting, so thank you for your answers.

My character is a Variant Human, Level 4 Battlemaster.

He has the Sharpshooter and Crossbow Expert feat.

As you can tell, yes, he uses a crossbow.

I am thinking about taking a level 3 or less dip into another class and I was wondering what you would in my position and why would you do it?

[PeteNutButter]

It's hard to say without more details. What are your stats? Your group? Your build intentions?

You definitely want to stay at least one more level for extra attack, possibly until 6th for that ASI, as +2 Dex is a great value.

[leogobsin]

Rogue would be a solid choice, mostly for Sneak Attack (some extra proficiencies and Expertise don't hurt either). I would say probably go either one or three levels in Rogue, 2 only gets you Cunning Action which may or may not be useful, but 3 bumps Sneak Attack up to 2d6 and gets you a Roguish Archetype.
Speaking of Archetypes, Scout is probably the most obvious for a ranged combat focus (and gets you extra expertise skills), Assassin could also be nice (I'm not a big fan of Assassin but you can't deny it's great for damage) and Arcane Trickster would be interesting if you're into the idea of invisible Mage Hand shenanigans.

[Speely]

Hunter Ranger 3 for another style and Colossus Slayer (Defense for the style if you already have Archery, which I assume you do,) and Hunters Mark. Also, some other useful spells to choose from.

[Malifice]

Hello Guys and Gals, This is my first time posting, so thank you for your answers.

My character is a Variant Human, Level 4 Battlemaster.

He has the Sharpshooter and Crossbow Expert feat.

As you can tell, yes, he uses a crossbow.

I am thinking about taking a level 3 or less dip into another class and I was wondering what you would in my position and why would you do it?

Not before you hit 5th level for extra attack.

After then, go nuts.

[Foxolicious]

Not before you hit 5th level for extra attack.

After then, go nuts.

Agreed get that extra attack at 5 before anything possibly 6 for that extra feat or stat bump

[CTurbo]

Definitely not before level 5!

I say 3 levels of Ranger for Defense Style, Hunters Mark, and Horde Breaker or Colossus Slayer. Bonus points if you can use UA Revised Ranger.

Gloom Stalker 3 is really good too for the same above reasons but trades Horde Breaker or Colossus Slayer for a super powered first turn and extra far Darkvision.

Rogue is always good. I might even take 5-9 levels of Rogue if you went this route because the class offers something great nearly every level. Scout is good, but you're probably tough enough not to really need to move away from enemies so that might by a waste. Assassin is very strong for archers since it's so easy to surprise enemies from range.

[Malifice]

My rule is never MC before 5th level if you can avoid it.

Barring a few corner cases (Fighter 1 for Bladelocks that are not Hexblades and a few others) its never worth delaying extra attack, stunning fist, font of inspiration, access to 3rd level spells (revivify, fireball, hypnotic pattern, counterspell, fly, haste, spirit guardians etc) , uncanny dodge etc.

Those abilities are game changers. They provide exponential leaps in power.

[Citan]

Hello Guys and Gals, This is my first time posting, so thank you for your answers.

My character is a Variant Human, Level 4 Battlemaster.

He has the Sharpshooter and Crossbow Expert feat.

As you can tell, yes, he uses a crossbow.

I am thinking about taking a level 3 or less dip into another class and I was wondering what you would in my position and why would you do it?
Hi!

Well, usually I pick multiclass because I want something specific.
And I probably wouldn't pick it before getting Extra Attack as a Fighter most cases (level 5).

With that said...
- Barbarian 2-3 (Bear): great way to make you even tankier than before, as long as you still play like a regular Fighter (read: don't think you're immortal just because you resist damage).
- Life Cleric 1 / Shepherd Druid 2: Bless / Healing Words / Goodberries for you and friends, advantage on STR checks, lots of utility spells...
- Rogue 2-3 (Thief/AT): because Expertise is always great, and Cunning Action helps keeping the ideal distance between you and enemies (or in your case, hiding).
- Warlock 3 (Tome, whatever Patron): Mirror Image twice per short rest will help you with that high DEX, you get plenty of cantrips and useful rituals too.

Annnnd that's about it for "generic" multiclasses for a Battlemaster.
Beyond that, any class can be a good choice depending on what you want that you can't have as a pure Fighter. :)