Gears are items that the hero wears. Later in the game boosted knights become more valuable and paladins a kind of obsolete. First, for every paladin you can spawn three knights. Knights are very good in offense, taking out towers (with exception of firebolt and lightning tower), tough barricades and even for taking out all other kind of troops.
Paladins are weak to ice and poison, so they are easily whiped out. Use of frosters, blizzard, frenzies, mummy, mortar is enough to get rid of them. So it’s a bit of a waste of pearls to invest in paladins.
To answer the question of forges. It doesn’t matter and you don’t need to max anything that is forgable first, the improvement of the forge is always calculated after primary statistic. Take for example pyromancer with range 4. When maxed that range is 5. Say we improve the range with 10%
- Start to forge when primary range is 4. Forge 10% (range becomes 4.4). Then upgrade pyro to max. This makes primary range 5, 10% of that makes 5.5 in total and not 5.4!
- Upgrade froster to max, primary range is 5. Then forge 10% -> range becomes 5.5
So it doesn’ matter when you forge.