Never use rubber mounts. You want your bike to vibrate because that's less stress on the engine and mounting hardware. Get a good seat and maybe a suspension seatpost.
Don't focus only on the engine. Bike first, motor second. Make sure all of the bearings on your bike are well greased and everything is adjusted properly.
The torque specs are for a 100% cold engine. Even a bit of warmth affects the torque specs of aluminum and can results in stripping.
Never ride with only a coaster brake. In your case, upgrading to dual pivot rim brakes is cheap and good insurance.
Never ride without a motorcycle helmet and gloves at the minimum
Never use fenders that are only held by a tab (Your fenders should be okay. Use blue loctite)
Never ignore strange sounds. Some components have natural play, learn to identify those sounds (IE: clutch plate)
Never ride aggressively. A slight tap of your wheel can result in death.
Create a strict maintenance schedule
Use a hub sprocket adapter
Take your time to break in the engine with the proper oil ratio. Don't rush things.
Torque everything to spec (while the motor is cold)
Grease the bearings
Either remove the tensioner and try to get the tension right or upgrade to the spring tensioner that connects to the case
Upgrade the gaskets
Replace the garbage chinesium screws with steel hex screws.
Replace the spark plug with an NGK and the spark wire with an automotive wire. (Very cheap and easy)
Seal the magneto area with silicone
Use blue loctite on the bevel gear screw, tighten it with a screwdriver and then drive it in with an impact screwdriver
Put a bit of grease on the gears
Liberally use loctite blue and nyloc nuts and let the loctite cure for a full 24 hours.
(optional) Install heli-coils. A little overkill and pricey, but much stronger than aluminum threads.
Use the exhaust strap that comes with the kit you bought. It will greatly reduce the stress on your exhaust mount.
Use automotive 3/16 fuel line. You can buy it in bulk from any automotive store and it will last much longer.
Wrap plastic wire loom around your fuel line. It will protect it from UV
Upgrade your connectors and use a heat sleeve to protect your wires
Clean your fuel tank before using it or buy a pack of fuel filters and replace it somewhat frequently during break in
Tune your carb for the proper fuel:air ratio. Running too lean can cause serious damage to your engine.