This will be a good method
if
BTC -
18000 buy lot 1 ,
15000 buy lots 2 ,
10000 buy lots 3 ,
9000 buy lots 4 ,
7000 buy lots 5 ,
5000 buy lots 6 ,
3000 buy lots 7 ,
2000 buy lots 8 ,
1000 buy lots 9 ,
500 buy lots as much as possible