Keep lab busy, max your favourite troop, spare de on heros
1 keep your lab busy 24/7. You only have 1 lab and there are over 2 years of upgrades to grind through, so as long as your lab is always busy you are making good progress 😃.
2 upgrade order doesnt matter too much, just use whatever troops/spells you have maxed and don't use nonmaxed (for your level) troops. Every time you max a troop include it in your army, try it out. Contrary to most opinions, ALL troops and spells are useful. 👊
3 upgrade heros whenever you have spare de and your lab is busy 👍 heros ultimately are the key to easy attacking - easy farming, easy war wins, easy pushing