First time on a high rate, you'll be in for a lot of change. Some tips not necessarily tied to high rate but rather just tips in general is to try to make some friends, find a guild, and start doing the basic quests here. First I'd start off with the Forsaken Knight quest. The guide can be found on the wiki. Then the Legendary Zodiac Aurora, then Rucksack. Both of those quests can be found at NPC's in the Knight Hall.
As for a first character, it all depends on what you want to do here. Before you dive straight into PvP / WoE you might want to hunt some MVP cards for your gear.
For MVP I reccomend Champion/Sniper. Both will do well. You can check the MVP's properties you are hunting on ratemyserver.net to see what arrows to use. If instead of MVPing you can also farm, I prefer Wizard for this. Farming, if you are unaware, is hunting x amount of items for x player for x amount of tokens [in game currency].
And in regard to high rate specifically, some things you will have to get used to is skill spamming. Kiel card's are used by almost every class to be able to spam certain skills at a fast rate. Also yggdrasil berries / seeds are very common here and during WoE / PvP will have to be spammed heavily, [there is no delay on this server]. Also, most MVP cards are common and most can be found for a somewhat affordable price, discluding Thanatos.
If you have any other questions my in game name is Special. I'm not as active as I used to be but still log on occasionally. Or if you have any questions you can just respond to my post here . Hope you enjoy fRO. =]