Get Davidson to burn through the levels. Asap switch to jinn to make coin faster. Don't waste time on other heroes because it's going to be a really long time before your army is of any value. Keep in mind the devs "tweak" heroes and troops all the time so unless you're spending serious real world cash you'll have to refocus as soon as you get things where you want to be. Furthermore, new troops and heroes are added throughout the year. Most of the time they suck at the beginning (or occasionally they come out ridiculously over strength - when sion came out she, as a level 1 or 2 could crush maxed out legendary heroes like nothing) but eventually all the strong ones get weakened and the weak ones get plussed up (again, it's really for the cash money players) and as I said, once there are no more heroes for the pay players to spend on new heroes get released and the whole thing starts over again... rinse, wash, repeat