If you want to work together with others to get items, go for it. It is much more fun and entertaining than single-player. However, there will be some people out there that don't respect teamwork from time to time.
Suggestions? You could always try reading the pinned topics up top of the boards. They cover a lot. Because the game is two years old, you might want to find some friends that play this game or else the "Unable to find any teams" will annoy you to no ends.
DLC chapters? Well, this order is based on my view. Chapter 10 is the most commonly played DLC online because of all the good items it has and how hard it is. Chapter 11 has Fuma gear for whip-users. Chapter 7 has the Miser Ring for high damage output. Chapter 9 has Sonic Boots for the fastest speed. Chapter 8 has Simon's Cloak for whip-users.
DLC characters? Personally, I bought all the DLC characters because I got tired of seeing axe knights moving ridiculously about. Dying in a lobby full of them and trying to figure out which one has the Water of Life can be tragic sometimes.
This game doesn't have much of a storyline (or a tutorial for that matter) so you are either on your own to figure it out or find some help. I'd highly recommend playing other Castlevania games if you come to like playing a specific character and want to know more about them. So there ya go. Happy hunting!
"The things I do for love..." - Courage, The Cowardly Dog GT: PC20XX
Well, if you want people to run with, you could add me. GT is the same as my forum name, shadowdragoon66. You can also make your way to the Alternate Harmony forums and find a whole lot more people that might be willing to play CV:HD with you.