#JavaScript, 114 bytes
This is my first entry in a codegolf contest! Please tell me how to improve.
x="repeat";y=n=>{return a=!n?"$$\\varphi=1+\\dots$$":"$$\\varphi="+"1+\\cfrac1{"[x](n)+"1+\\ddots"+"}"[x](n)+"$$"}
Paste into browser console and call as f(n)
where n
is the number of 'steps'.
Simplified code:
var x = "repeat";
function y(n) {
if(n === 0) {
return "$$\\varphi=1+\\dots$$";
} else {
return "$$\\varphi=" + "1+\\cfrac1{".repeat(n) + "1+\\ddots"+"}".repeat(n)+"$$";
} // ^in golfed version, String.repeat(n)
// is called as String[x](n)
}