Thanks for the question. According to me, India and US are currently the best countries to invest for long term if you want to grow your wealth.
India is a fast growing economy and the Government here is heavily pushing to achieve its dream of becoming a trillion dollar economy. So you can expect good growth in the next 10–15 years. For investment, you can choose from a variety of equity and fixed income instruments based on your risk appetite. Some common equity instruments are stocks and mutual funds. On the other hand for fixed income instruments, you can look to invest in PPF, fixed deposits, recurring deposits, etc.
On the other hand, US is also growing its economy at a decent pace. This inspite of its being already the leading economy in the world. The RBI has provided an option for Indian investors to invest in the US stock market through its Liberalized Remittance Scheme(LRS). As per the scheme, in a financial year an Indian investor can send money to US upto $12,500 for investment purposes. With the help of this scheme, Indian investors can easily invest in the stocks of top US companies. Check out the below article if you want to know more about the same,