Firstly I think we can categorise this into two
1. The profit suckers: they tend to offer but gain from you instead, they make alot by giving false hope but they reward little .
2. The scammers: this category only look for ways to lure people using attractive ads thus scamming those who fall for it.
Well we have some ads with just pure advertisements of their company or products
My advice: Engage with caution in any ads that deals with deposition of funds. I won't say you should completely ignore because not all are scam sometimes but 60% tends to be scam .
In addition, avoid any site asking for wallet phrase( it's a pure scam )