Using gamma as the name of a variable is a bad idea. Regardless,...
Where is the problem? Just substitute a range of values for gamma. Save the solution for each gamma. Then plot, with gamma on the x axis, and your solution on the y axis. WTP?
You can even use tools like fimplicit, which will do the hard work for you. For example,
f = @(gam,y) gam.^2 - y.^2 - 2*gam.*y.^3 + gam.*y + 1;