Hello there! Christmas time is coming and i decided to buy new gear! I currently own a Fender Stratocaster, and a humble Vox VT30 amp. I'm just a bedroom guitarists with no plans of joining a band.

I like almost all types of music but i like Metal and alternative stuff the most. So anyway back on topic i just got some money and i decided to burn it in buying either the POD HD500, a new amp or a new guitar.

My budget is 800 - 850.

I'm interested in the POD since it has all those effects and amp models which will give me plenty of stuff to experiment with and get some weird sounds from it.

A new amp would also be great since the Vox VT30 doesn't give me the distortion for metal i want bu for everything else is great.
800-850 what? flamingoes?
Gibson Les Paul Studio
Highway One Telecaster
Dean Evo
Mesa F-50
Laney GH50L
Vox AC30 C2
Ampeg V2
You can get a lot of amp for 800 bucks. It may not do much if you put the POD in front of a modeling amp. I think they have a headphone out on it, so that may work.
A new guitar won't get you the sound you are looking for in the metal distortion.
Maybe someone else knows: Can you put a Cab on the HD? Does that work?
Harmony: Stratocaster
Alvarez: F-200
Schecter: Omen 6
Fender: BXR-60
Dean: Metalman Z Bass (Betty)
Egnator: Tweaker 15
Pearl: Maximum
Custom: Harley Quinn Bass
Custom: TK-421 Explorer
A steadily growing supply of pedals
I just wanted to put two cents (US) in.

Be aware that ANY effects box or pedal that has amp modeling will NOT necessarily sound like the amp it claims if you connect its output(s) to any guitar amp, regardless of which one.

Remember, all guitar amps already "model" a sound type: their own.

I have a high-end ($8,000), professional, multi-effects rack. Its outputs go to very "flat" response powered speakers (QSC and various others depending on the venue). Even then, it doesn't perfectly sound like a Marshall Plexi, or whatever.
Get a mesa mark IV combo. You may feel the need for a boost but its a good platform for a lot of things. Good cleans, good mid-gain, good on heavy side alone but some people like boosting it.
If you are mainly a bedroom player you would be well served with an POD HD500 + a monitor. You can add a decent set headsets for quiet playing at night.

That being said, you can also go for an amp that has some versatility, the Mark IV suggested above is a great amp to look at with plenty of tonal options. Id also suggest a Peavey JSX/XXX or even a Carvin V3 or Legacy (used).
-Carvin CS6
-Carvin DC4 w/ Bigsby
-Takamine EG530SC
-Seagull S12QI

-Orange Rockerverb 50 MKII
-Carvin V3MC
Standard strats are great guitars. I'd put off upgrading guitars, as you can make a strat do anything. Pod's are OK. I personally think an eleven rack sounds much better, even though it has less effects, they're realistic usable ones, not like 4 ring modulators, haha. And they're about the same price now and include protools so you can recor things.

I'd go eleven rack+Powered monitor of some type

I recently plugged in my vt50 for like the first time in 3 years and thought it sounded terrible compared to both the pod and eleven. So either way you go is an upgrade.