I play under a specific set of rules as a F2P Solo challenge player:
1.
ONLY ONE CHARACTER!
2. If I
CAN solo something, I
HAVE TO solo it.
3. I can earn an achievement with others' help as long as I
DON'T DIRECTLY ASK FOR HELP to earn it (ex. killing a world boss by attacking it while another player happens to also be attacking it)
4. If it
ABSOLUTELY REQUIRES a second player in a group to complete (ex. The Masquerade achievement from Hallow's End), I can use a second F2P account to do it.
5. I can queue for PvP battlegrounds as long as I
QUEUE SOLO.
6.
NO DUNGEON QUEUES until the dungeons I can queue for are soloed (I have succeeded in this!).
These are additional challenges that can be taken for a more challenging experience:
1.
ONLY ONE SPECIALIZATION. This will make it easier to gear up, but not all specializations (or classes) can solo everything, specifically dungeons.
2.
ONLY ONE TALENT. Easier for some classes as not all talents are good.
3.
READ EVERY QUEST! There's no achievement for it, only personal. Learn the lore of WoW!
I'm basically trying my best to solo as much of the game as possible on just one character. That includes gearing and exploration, which means the best gear may be unobtainable and some zones will never be visited.
If you are interested in knowing what stuff is solo-able, my hunter account would be a great reference! I follow my rules
VERY STRICTLY to show just how much content a F2P account can complete ALONE!
Click here to see a link to my Hunter!
UPDATE: A lot of time has passed. I no longer play the hunter, but it still followed all of the above rules perfectly. Good luck out there!