If fitting brushless, then fit a steel gear set from the off, axial or Robinson racing. There is a cheaper new set out too but I can't find the link at the minute.
Fit a slash 32dp 54t spur gear and a 12t pinion
When building the props, fill the void in the male halves with a rod or dowel (not too tight or it will cause the props to bind and you'll never get it out if you need access to the screw that holds the ends on) and use a cut off piece of one of the spare female parts to sleeve the exposed male one to add strength and prevent them from collapsing on themselves.
Maybe look at alloy front hubs,C's and rear lock outs, go axial or vanquish as the others can be a bit hit or miss on quality.
Fit a separate BEC, I only use castle ones and have never been let down, and go for the strongest servo you can, at least 20kg+ on 6v. (Hitec 7450/7455 on mine and my sons.
Other than that, you should be okay. From here I would just upgrade as things break.