Buddy modifications are divided into two categories:
Concerning Ravi Piaggio there are some performance mods that you can do
Ignition coil, Plug wire, Plug: This is the most common mod found in most Ravi Piaggio's. I myself have done this mod. The difference i feel after installation is slight increase in pick and Slight increase in bikes power (No it wont become rocket).. You can buy this combo from Lahore with the help of @vickytulla ranging from 2000-2500rs
Fuel Additives: Although i wont recommend it, but still you can use fuel additives like STP OCTANE BOOSTER to gain temporary advantage in performance. A bottle costs around 450rs enough for 45 litres of petrol. You will feel difference in pick and top speed
Tyre: You can switch to big size tyres like 100/90, you will feel good grip and bike looks monstrous with big tyre but again it has some side effects to. Acceleration and topspeed will be decreased as in my case it dropped by 15km/h. You will also notice slight increase in fuel consumption. A good 100/90 tyre will cost you 4000rs
Removing rear fender: I suggest you to only do this if you install bigger size tyre or else it will look odd
Clip ons: Clip on handle bars give bike a sporty look. There are two type of clip ons that can be installed on Ravi Piaggio i.e flat and raised. Flat clip ons are fun to drive with, gives agressive posture but long term riding will cause shoulder and back pain. On the other hand raised clip ons are comfortable. They will cost from 2500-3500 depending on availability
Alloy rims: surely they are eye catching but there is no fun of installing them unless you got original Japanese alloy rims. They will also reduce the acceleration of the bike. Will cost around 10000rs
Side fenders: Depending on thier availability they can cost from 2000-3000rs. But again the main disadvantage is air blocking for engine.
Carbon fiber wrap: Cost around 80rs per sq ft. You wrap different parts of your bike for cosmetic looks.
Members that might help you finding stuff or guidelines
Some threads for your reference that might help you:
Hope i answered your query. Feel free to ask any more question (If any)