Salvage anything green, blue, or white in your inventory. Salvage yellows that sell for less than one ectoplasm, otherwise sell them on the trading post. Keep your gold exotics until you’ve researched them.
Deposit your collectibles, sell your runes and sigils on the trading post.
Your first goal is to obtain exotic level 80 Berserker armor. This will be sufficient for any PVE content apart from fractals. Later you can upgrade to ascended armor, but it’s not really necessary.
If you have any tokens from running Citadel of Flame, Crucible of Eternity, or WvW then cash those in (for WvW, make sure you select level 80 armor since they sell lower levels too.) Then go to the trading post and buy any pieces you are still missing. You may need to grind for some gold and/or sell materials to complete your set, since it’s kind of expensive.
Once you’ve got armor, start looking for exotic level 80 Berserker weapons. By this point hopefully you’ve decided on a set or two that makes you comfortable. Again, you can later upgrade to ascended weapons but it’s not necessary.
While you’re gearing up, you should experiment with different traits, runes, and sigils. There are plenty of guides floating around that might match your style. Some runes and sigils are very expensive, so play with the cheaper ones first. No rune/sigil set is absolutely necessary in PvE.
Finally, start grinding for ascended Berserker rings/amulets/accessories. Unlike ascended armor and weapons, you can buy these from merchants.
The only time you’ll need to buy non-Berserker set is for WvW. You might also use a different set for PvP, but those are always free.