As a new player starting from scratch is there anything . . .

I need to purchase? I started the f2p last night and I am impressed. Is there anything I need to be aware of?

As a Free to Play fresh account you have access to everything from Expansions up to Sentinels Fate. You have the usual F2P restrictions in that you cannot wear LEGENDARY or FABLED marked gear. You also would need to purchase Chains of Eternity to gain access to Destiny of Velious, Skyshrine and Chains of Eternity content. If you wish to use Mercenaries or play the Beastlord class you also need to purchase Age of Discovery.

CoE is $40
AoD is $40

Neither is a necessity until you hit lvl 90. CoE raises the AA cap to 320 and level cap to 95 though without that you will be stuck at 280 and 90 for AA and Level.

If you like it, I'd spend the $5 and buy something (doesn't matter what) from the SC store to become a 'Silver' member. That's not a monthly thing - spend $5 and you're silver forever. You still have restrictions, but it will make your life a little easier.

If you're not grouping a lot, mercs can make the low going easier (way too easy in many cases though), so you might want to buy AoD before you hit max level. There's no reason to buy CoE before then.

Estred was close but with out COE you are stuck at 90/250 and aod lets you get 90/270 so you need to buy coe to do anything end game.

True, it was AoD which lifts AA limit +20 not CoE ^^
But to start with the game, i would suggest, buying AoD, as mercs are at the start can help alot.
CoE you need only when you reach 90, then you should think about a subscritption.

When did this happen? I thought it was spend 500 SC in the store to buy a Silver membership, ON the Silver membership.

Unless they changed it, you still have to spend $5 to buy the Silver membership. Which to be honest is a great value when you consider all you get for a one time fee.

Most of the low level Legendary/Fabled gear isn't much better than the revised Treasured quest/Mastercrafted gear now. You could easily make it into the 50+ range before the real advantages of having a Gold membership are needed. But depending on you Race/Class choice and your playing habits, going with a Gold subscription might be more cost effective than buying unlockers.

I would also recommend AoD as your first expansion (not really an expansion though). The Mercs make leveling much easier when groups are harder to find at low level.

Yup, as said earlier, buy silver membership for 500sc. It takes some restrictions away and makes it more enjoyable.

If you can afford to buy AoD expansion, then do, it's worth it for mercenaries.

Don't bother with CoE until you are near level 90 or have 250AAs.

If you buy a subscription then everything (bar the expansions mentioned) is available to you.