What, exactly, is voltage?
I suspect I'm just going to confuse you further, but here goes:

Some of them say that voltage is like pressure, others say that voltage is is like gravitational potential energy and then some say its a measure of electric field strength.

We say that voltage is like pressure, or like gravitational potential energy, because we're trying to draw an analogy to something that you can see or feel (because you can drop a rock on your toe, or feel the pressure in a balloon when you blow it up).
What voltage is gets abstract (hence the analogies).  If you have an electron in an electric field, there's a force on it, so it wants to move.  If you had a pair of magic tweezers that would let you grab that electron and move it from one spot to another, you'd have to exert force on it -- putting energy into the system -- or it would exert force on you -- taking energy out of the system and delivering it to you.
A volt isn't a measure of the electric field.  Volts are a consequence of electric fields, but the electric field is in units of volts per meter.  What a volt is is an expression of the amount of energy available per unit of charge.  So if you have one Coulomb of charge, and you let that charge flow through something that drops one Volt, then that charge will deliver one Joule of energy to whatever that something is that was dropping one volt.

And also if voltage is like gravitational potential energy, how does more voltage mean more current?

And here our nice analogy breaks down.  In this sense voltage is more like pressure in a water pipe.
For all physical things, if you put a voltage across them current will flow -- it may be a lot, it may be minuscule, but current will almost always flow.  For most things (there are some exceptions), the more voltage you put on it, the more current will flow.
So in this regard, voltage is like pressure in a water pipe -- more pressure equals more flow, just as more voltage across a resistor equals more current in the resistor.  But this is just an analogy.  Ultimately, you just have to beat your brain against the physics until everything becomes intuitive, just as you learned that when you let go of something it falls down every time.  The difference is that you learned the lesson about dropping things before you were a year old; the voltage lesson comes a bit later in life, so you have to purposely let your brain flex.