I think that the amount of coins that the project allocates for airdrop can reach up to 20% of the total supply. This way you can attract the attention of a very large number of investors to your coin. It is very important that the number of coins that each airdrop participant receives in terms of dollars is the same at the start of trading as it was declared during giveaway. This will create a reliable image of the project and strengthen its position in the market.