Making a class/actor's TP gauge start empty and fill as they attack and are attacked?

I'm making a dungeon crawler to help learn the program before tackling bigger projects and I have only 4 characters, each is set to their own class. One of the characters/classes is like a berserker and I was wondering if it's possible to set that one's TP gauge to empty and to increase by X amount or X% each time they attack/use a skill in battle or get attacked? Then once it reached X% full that character's attack is doubled, but their accuracy/hit rate is lower? Or maybe have a skill that would cost X% TP that would do that? I'd also want/need their tp getting refilled at inns, etc to be disabled. Would I need a plugin for this?

Yes, no, maybe.

The Event Command "Change TP" is there for you.

On Database > Skills:
Create A Berserker Attack.
Go to its Effects
Double click to make an effect
Choose Other.
See that Common Event Feature?
You can select one.

Back to Database main menu.
Choose Common Events.
Make a Common Event named: Brsrk_TP_attack.
Inside there you can use Event Commands accordingly to increase for each hit.
Then on the Attach Attack you add the Effect of calling Brsrk_TP_attack and there you havce it.

So yes I think this is 100% possible with eventing, but if there is a plugin that does it in a more neat way, I would go for that.

You lost me and I got totally confused at this point. :yswt2: Should I add a "change state" and create a state doing what I want it to do?

Attack*
Not attach

You make Common Event that handles the TP.
Then you call the Common Event, by using a skill. An ATTACK SKILL for the berserker.
You call the event from the Effects (in the Skill menu). Double clicking on the Effects list, you can create a new effect. Choose the "Other" tab. There will be an option there to call a common event.

By default:

• TP initialises to a random number from 0~24 at battle start;
• When a battler is hit their TP increases by half the HP% damage multiplied by their TP charge rate (tcr),
  i.e. if 50 damage is dealt to a battler with 250 max HP and standard (i.e. 1.0) tcr, that battler's TP should increase by 10;
• The Recover All event command (inns?) should not affect TP.

I'm not sure when you're wanting the TP to "empty", but I think eventing like @Dreadshadow describes should be able to handle it. If you're open to using plugins Yanfly has an Enhanced TP plugin that gives you a lot more control over TP, but it does require a bit of setup.

For the special effects when you reach full TP...you could use troop events to add a "powerup" state when a battler has full TP, but it would be grossly inefficient as you'd need the event in all troops and with Moment Scope (i.e. a "parallel battle event") to accommodate TP charging mid-turn. I'd recommend something like Yanfly's Auto Passive States plugin, which offers a <Custom Passive Condition> notetag: