Notes:
Gangster always faces Elite Waves and won't see any Horde Waves when playing on higher Danger Levels
Gangster cannot find items with the Lock tag. This is currently just Fish Hook.
Stealing Items:
Gangster can steal one item during each shop. But in return you cannot lock items. (They use the same button). Efficient use of the Steal ability will put you ahead on items, even with the 20% increased shop prices.
However, stealing an item comes with the risk of spawning an elite during the next wave.
Chance of Elite spawning: Wave ⋅ Item Tier ⋅ Item Price / 120
Stealing chance is rounded to nearest 0.1% and cannot go above 95% chance to spawn an elite.
Stealing chance is affected by Shop Price, so Coupon.png Coupon decreases the chance. But remember that Gangster starts with +20% Shop prices.
Spawning an Elite:
When you steal an item and get caught, the Elite symbol shows up, and a growl can be heard. During the next wave, an additional elite will show up. If you get caught before an Elite Wave or before the Bosses, you're in for a hard fight. The elite will show up in addition to the default elite or boss/es.
Killing any Elite, spawned from the Shop, or one of the baseline elites from the Elite Wave, will increase the HP of any future elite/boss by 15%, and their damage by 7.5%
So if you kill the 3 Elites and maybe 2 extra that you've spawned with the shop, that's +75% HP and +37.5% Damage for the Bosses. Elite and Bosses HP Modifiers
In addition to Gangster's ability to increase Elite/Boss health, there's also some modifiers that are present in all games for all characters.
Elites have reduced health on earlier waves: 50% HP from wave 1-8, 75% HP wave 9-12, and 100% HP wave 13+
These are multiplicative with your +15%/+7.5% on kill ability.
This makes it quite possible to actually kill elites in the early game.
Also remember that Elite's HP scale linearly with waves. See Enemies.