1) Finish leveling Kael to 60. Get him fully ascended. Use gems to unlock his masteries. Fully book him. Give him Lifesteal gear so he can solo farm Campaign Brutal 12-3.
2) Use Kael + 3 food champs to level the food. Use food to rank up other food. Repeat until you're able to rank up the champs you care about. Bring those champs to 60. Get them fully ascended, and use gems to unlock their masteries as well. The champs you'll want to level are:
3) Farm Dragon for gear. Do this for a long, long time. As your gear gets better, start doing higher and higher Dragon levels. Try to do 16 until you're able to do 20. Don't bother with any other dungeons until you're able to do Dragon 20 reliably.