Tips for a new player (WvW)

Hi folks, I am new player in GW2 and playing as a thief, WvW is really fun and I love playing it. I came to a conclusion that an open 1v1 fight is never favored for me as a thief, or at least I am not that skilled, so with my mobility and stealth I go roaming and can help my friends turning the duels into 2v1.I am playing deadeye thief, d/p and rifle, equipped myself with full exotic berserker armor and trinkets. I have sigil of force on the dagger, sigil of air on the pistol and sigil of force and sigil of energy on my rifle. My health is an issue yes, but I manage to break out of fights and keep myself alive using dodge and stealth.

1. Should I switch to marauder armor set and keep the trinkets berskerker stats?
2. I am planning to buy Call of the Wild ascended amulet (157 power 108 Precision 108 Ferocity) what to add on the enrichment slot and best way to get it? Is there an option to add another slot on ascended amulet?
3. I am planning to Buy ascended Ring of red death (126 power 85 Precision 85 ferocity) what to add on the infusion slot and best way to get it? Is there an option to add another slot on ascended ring?

It depends on what play style you like. Super damage with full zerker gear? Even with marauder deadeye is more than capable of landing great damage. I usually play a core sword dagger thief. But sometimes i like to switch to deadeye. I use a full marauder set with valkyrie weapons. Runes of strength with strength sigil and might on dodge food. I get the 5% damage from runes plus a huge amount of might. But with deadeye i had great results with marauder armor and weapons plus zerk accesoriess and scholar runes. In the end is what you like most.....On amulets you can't add a second infusion slot. You can add wvw enrichment infusion. You can buy that from WvW Laurel Merchants for 5 Laurel + 125 Badge of Hono, or from a Skirmish Supervisor for 45 WvW Tournament Claim Ticket + 20 Memory of Battle. For the rings second infusion slot take a look here : https://wiki.guildwars2.com/wiki/Attuned_equipment . Best infusion would be mighty wvw infusion.
Also check https://metabattle.com/wiki/Thief. Is really good place to start from.Good luck.

depending on how you play, going full valkyre is also an option when using hidden killer. because if you never stay visible long in a fight, then you dont need any further precision. you then do more damage on valkyre than you would with marauder while also having more health.

infusions are not that important for fighting players but if you go all offensive WvW infusions, you can have a very noticable damage boost against NPCs.