Playing as Man C isn't bad but asking who to sign is. Even if you have no clue, there is an entire subforum dedicated to good players, who you can sign as Man C cause you got the money.
The biggest challenge in the game is bringing your team up to par with the big teams in the league (or promotion for the smaller clubs). It's easier and faster with Man C than with Sunderland, but doable with both. I do agree though with the statement of the Spanish guy, that keeping your team in the top is a challenge. You can start with Man U, but if you screw up you'll get sacked while playing with lesser clubs gives you more options to fail. Sure you can buy every player in the game which will make it easier, but you are then expected to go for the title, which with all obligations in England can be hard. However I tend to stop as soon as I won a quadruple (league, 2 cups and the CL).
Anyway, Man C is a great way to get into the game, but then I still don't buy the absolute topplayers (Ronaldo, Messi) but the players just below that. That is still challenge enough in a first game. Players can fail, refuse to gel, redundant players get angry or unsettled by the press, you have a board with unrealistic wishes and a lot of keyplayers (who won't come for less) to manage.
In my first season now. Bought 8 (!) players (2 panic buys cause of long defensive injuries though) and still just aiming for CL qualification. For those interessted in who to sign: Veloso (DMC), Vukinic(AMC), Kuzmanovic (midfielder Udinese), Zapata (DC), Vagner Love (ST), Diarra (DMC, shouldn't have but they were letting him go for 5 mln), Vertonghen (DC), and this multifunctional wingback from Rubin, Brazilian kid forgot his name. Btw if you relegate with Man C you need to play another game.