I hope you´ll get one soon! Yes, the Challenge Portals are great, along with Black Friday summons too, as they contain no S1s, so the odds of getting a unqiue none S1 hero are better, though, many S1s are really ok, especially with their costume bonus, so I recommend the masquerade portal too. I use mine all the time still.
I´ve always been C2P - followed by F2P for a long time now, and whether that´s your thing or not, I wish you the best of luck on your summons!
I have played with this combo for most of my map stages, with Cad, Wu Kong, Li Xiu making the team depending on the situations. With some battle items being used intelligently, this will get you through to Season 5. But you do need to go for C Colen’s defence/health emblem path, and use Kiril, Wu Kong, Boldtusk or C Rigard to boost his attack before he fires his special. Intelligent use of counter attackers would be helpful but they will be slow in getting you through the earlier waves. So to clear the earlier waves, you need a rainbow team with strong attacks or attack all in most cases but do remember to prepare mana for all your heroes just before the Boss wave. Use minor mana potion sparingly where the situation requires it. Otherwise try to save your battle items as this would allow you to upgrade your buildings and hasten your progress.