You've got a good start. Firstly, a bit of info on High Elves.
They're the weakest of the three elf books, but they're the best written books. This is evidenced by there being no netlist. Multiple people have written many excellent lists(I'd like to draw attention to the masterpiece that is Hristo's
UK Masters list).
This is because they've got a lot of strong choices across the board, and no weak choices. The reason they're weaker than the other books is that the other books have access to insanely good options(see Warlocks and Trueflight). But those are staples in every list(See the only Wood Elf tournament list.)
You've got a good army, and a good start. You just need to bulk up your units. As people stated above me, Sea Guard are, and I'm going to let Admiral Ackbar take it away for this one,
They've got shorter range than archers, and are more expensive. You pay more to get less out of a unit.
Swordsmasters are good, I'd probably use these guys as a unit of 7 or two units of 5. Hordes aren't really that strong anymore. They've got their Jedi save, which is a plus, I guess.
A good start for a competitive list is this:
Archmage, Level 4, light Book of Hoeth, Talisman of Preservation.
Mage, Dispel Scroll, light.
Mage, Light
Mage. Light.
Noble
BSB with the Armour of Caledor.
600 points of archers. (One big unit of 15-20 with Full command. The rest in units of 10 with musicians, Two have standards for B&G. Keep it as close to 600 as possible.)
Two units of 6 Dragon Princes with musicians and Champs. (Flanking units, or charge+Challenge and do wounds.)
24 White Lions with Full Command and the Banner of the World Dragon.
4 Bolt Throwers.
That SHOULD leave you some points to fit in some units of your choice, but that is a strong list that competes in all phases.