Those are more like add ons than mods but..
Firstly do you have all the tools you need to properly install the stock kit?
Torque wrench, appropriately sized sockets and wrenches, caliper, chain splitter, rotary tool with cut off wheels and grinding disc and burrs, enough allen key sets and spares of the small sizes, safety glasses and ear plugs, blue Loctite and red Loctite, red n tacky grease, standard lithium grease, synthetic two stroke oil for air cooled engines, a good supply of washers spacers and nyloc nuts, preferably a bicycle repair stand or something that will do the same job so you don't have to break your back lol.. I am sure I'm missing out loads of stuff I can't remember all at once.
Then think about the mounting hardware that you'll need to get the engine secure in your particular frame, and are the studs and bolts in your kit up to a decent standard or are they the chinesium ones as in the cheaper kits?
The rear sprocket wants to be directly lined up behind the engine sprocket so you might want to look at top hat adapters, or are you confident that the rag joint will be sufficient?
The short PVC fuel hose should be replaced with the right length, and silicone so it won't harden.
Then there's spares. If you're going to be running the standard CDI and stator you'll need to have at least one of each as a spare at all times.
Spare gaskets I would say are essential.
Then you can get a spare cylinder and rings. Oh don't forget the woodruff keys!
Still have some money left?
I would say my choice for a first add on would be a good head (and plug), not because they are claiming high compression but because it should be able to absorb and radiate the extra waste heat made by the other power increasing modifications you'll do later, and won't warp and crack.
The kit chain is very heavy and low quality. I would consider a narrower, lighter alternative as well as something higher quality.
36T is pretty small, and you might well have a better top speed, not just better acceleration and climbing, with a 40T or 41T rear sprocket.
Read as much as you can. Every day, every time you're waiting for the kettle to boil, every time you're watching TV and the adverts come on, absorb as much information as possible to get a good idea of what you are getting into, the common problems and mistakes, the theory and the techniques of building a good engine and a good safe bike that suits your requirements and purposes.. What are your requirements and purposes?
