For Firm Structure the related topics are:

1. Perfect Competition
2. Imperfect Competition

a) Monopoly
b) Oligopoly
c) Duopoly
d) Monopolistic Competition

And for the Producer's Equilibrium, the general rule is:

MC=MR
However, following topic is worth reading;

1. Iso-Quant / Iso-product / Equal-Product (all same thing) (Note: it is opposite of indifference curve in consumption theory)
2. Iso-cost line
3. Marginal Productivity Theories.

goodluck.