Build guide to increase action points per turn for mage?

[Tomas Schelbik]

I know that I can drink potion of haste and I have a lvl 3 haste spell, but the potions are rare and the spell consumes one spell slot and I have like only 3 of them. Melee fighters on the other hand have some build opportunities to permanently get a second action (or rather use bonus action as action). So what can I do as a mage to reliably have 2+ spell casts per turn without relying on haste?

[jonnin]

you can cast with your bonus action with metamagic. That is sorcerer though...

[Fluffykeith]

Do a multiclass dip into fighter for two levels, so get Action Surge.

[Detective Costeau]

There's really only Haste and Action Surge. An extra action is rare and intentionally hard to come by because it is incredibly powerful.
Also if you're diligent about checking merchants for gnoll ears (are they hyena ears? something's ears anyway) to brew haste potions and buying the already completed ones where you see them, Haste potions aren't really that rare.

[Sonrangeri]

As it was said before, you could go Fighter lvl 2 and get Action Surge, or if you need more extra actions (generic ones like disengage/dash), going rogue would help you with that. Potions also exist.

[Cimberly]

you can make a potion by yourself. if this method suits you, i can check recepie in my oldest walktrough. also you can steal it from a merchant, who sells it, a few bottles after every long rest/lvl up. i have like 10 potions at every character + a little bit more in storage right now, and i'm only lvl 6

[Pat Fenis]

Haste pots are abundant. Lot of hyena ears in act 1, buy more from vendors when you see them. Recruit random hireling and make them a transmuter wizard with medicine proficiency and high wisdom. Level as rogue for expertise after lvl 4. Increase wisdom with feats. Buff with enhance ability wisdom, guidance, and they should always be able to pass the medicine check. 1/400 chance to fail at level 9. It's a very high success chance before that but you will see the odd failure.

[InsaneDrunkenAngel]

You need sorcerer.
Twin cast Haste on you and your buddy of choice - that's one extra action.
Use quicken metamagic to cast one more spell per turn.
Drink bloodlust elixir to get extra action for a kill.
2 lvl fighter dip for action surge.