I have tried to participate in an IPO but it just told me that I needed to gain more equity, what is equity and how do I gain it. I already have double the equity that I am trying to participate in.
You need to have an equity of at least 20 million AS$ in order to participate in an IPO.
Simplifying a little bit here, but basically you build equity by making profits at the week ending date. Making losses cuts into your equity, so it is possible to actually have a negative equity (which doesn´t necessarily mean the company is financially unstable though, there are many reasons for a healthy company to have a negative equity in real life).
Oh sorry, I forgot something... As for:
what is equity
the (again, a little simplified, but fine for AirlineSim) equity is basically your balance total minus all loans.