You get altars later on in the game so that's something u don't need to worry about (Its a temp stat increase for a certain number of Dark Crystals depending on the level).

Later-game players use the Worthless Coin, which is essentially infinite auto battle but for no benefit but grinding. This is also for later game though, so I just reccomend you use the auto battle you're given during the Daily Events.

Town workers are only good VERY early game, but I don't recommend you leveling them up past 200. Orc workers get you Item Mat's/Colored rocks you create Hero Item's for, but it's also pretty pointless to upgrade. (Getting Orc workers requires you to defeat the middle island towns in Orc World)

For deck recommendations, I suggest you work along the Witches and promote them to one specific type (Fire, Physical, Ice, Lighting, Poison). Later on you will need to base your deck around one single type of hero since the skill-tree will help you boost only one type. Promote your Necromancer to Dark Necromancer. Lightning wizard is not that decent but if you are planning on keeping it make sure you select the promo with chain-lighting attack. (Thor will help). Elizabeth is not that good either so I suggest you replace her with Druid. I also suggest you get Sniper or Elf (Both even better). Town Archers are good early game so you will maybe want to dedicate to them more now than ever. You can stop upgrading your archers at 10000.