IMO, a build centered around dragon slash is a decent "burst" damage build as you call it. Just bring skills like silverwing slash, dragon slash (elite in factions, you can cap it in boreas seabed), healing signet, and the rest is really up to you. I would recommend a max furious sword mod and 16 swordsmanship (dragon slash takes 10 adrenaline to use and gives you 5 back, if you use the furious mod, which gives you double adrenaline with a 10% chance, you might be able to recharge dragon slash along with any other adrenaline skills you have). I'm sure there are better builds, but there's my 2 cents there.
in terms of getting farther in NF on a foreign character, you only need to follow the primary quests. Because you are a foreign character, you don't need to do all those little quests that you normally get in NF if you made a NF character (technically you can't even get those quests). There is a primary quest called A land of heroes which can be used to get a lot of sunspear points rather quickly for your factions character. in this quest, you get bounties for corsairs and kournan soldiers which give you 4 points for each one you kill. in this quest, the area is crawling with both. If you finish the quest, then abandon it before you accept the reward, you can go back to champion's dawn and do it again for more points until you get to sunspear commander, at which point you don't get the bounties anymore. then, just go through the quest normally and continue the storyline.
in terms of armor/weapons, if your character already has max armor (60 for monks, necros, elementalists, ritualists, and mesmers, 70 for rangers, assassins, and dervishes, and 80 for warriors and paragons) there is no reason to buy more armor unless you want to spend 15k a piece for armor that looks cooler. For the most part, you will want to either get collector weapons (basically the wal-marts of the GW world, theyre good and incredibly cheap, but since its not name brand, you won't seem 1337 to the "elite" players, you can look up "[put profession here] collector weapons" on gw.gamewikis.org and it will tell you where the collectors are and what item you need to collect in order to get their weapon). There are "green" weapons that are max damage and usually have good stats, but some are pretty exspensive (some swords are in the 30-40k range). I would suggest looking up "unique items quick reference" on gw.gamewikis.org to see what weapons you want to save up for, there is also a price check forum so you can find out how much to save up for that weapon.
If you ever need help in any of the games, feel free to PM me in game, my IGN is kartok the swift. just know if i dont respond right away, chances are i have GW minimized or im not looking at the screen, so dont think im ignoring you. hope this helps, enjoy!
EDIT- i gotta learn to proofread faster, 2 people beat me to the answer