With your 25g, you can go on the trading post and buy all 6 peices of exotic(orange) berserker armor (head, shoulders, chest, gloves, legs, boots). Berserker armor has the stats 'Power', 'Precision' and 'Critical Damage'. Just make sure to put in buy orders
(otherwise known as 'place custom offer') as they are a gold or so cheaper(each). Just click the beige writting on the left side that says "place a custom offer" and outbid what ever the highest offer is (just one copper higher is enough).
The armor on the trading post is called "Berserker's Draconic", make sure you get the heavy (plate) gear though
If you don't want to use your gold, you can instead buy masterwork (green) berserker armor for a few silver a piece. Point is, you need to gear yourself properly for a start.
Regardless, press 'O' to bring up the trading post screen, go to the third tab down (called 'Trading Post') and enter the word "berserker" in the search field and set the filter to 'Category: armor', 'Rarity: Exotic' (or masterwork), and 'Level Range: 80 to 80'.
Then buy masterwork (green) weapons and jewerly from the trading post. Get either Knight's (Toughness, power, precision), or soldiers (power, toughness, vitality) for all of that, depending on how much tankiness you want. As someone new, the extra defensive stats will help keep you alive. For weapons, I would suggest getting all of the following: longbow (or rifle), Greatsword, Axe (or sword) and shield. These will off you a nice variety of thing that will cover every situation you might run into. Alternatively, you can just grab what ever you find fun.
Then you can do dungeons, which will get you both gold (to buy new jewelery) and tokens (to buy weapons), and start replacing your masterwork(greens) with exotics(oranges). By the time you start replacing your gear, you'll probably feel more comfortable with the class and can replace the greens with berserker gear. You might want to spend some time playing in the open world doing w.e before going into a dungeon though.
There are other ways to get gear, such as crafting it yourself, WvW tokens, random drops, etc, but this is probably most straight forwards.
The others bring up a good point as well, keeping the warrior but starting a new character might be a good idea to get used to the game. Otherwise, if you just want to play your 80 warrior and are relatively comfortable, then you can of course just do that. Try to do map completion or join zergs to get a bit of extra currency(don't forget to gather!) and playtime experience before jumping into dungeons though.