What is the order of basicity of amines?

Tertiary amines are the most basic amines, then secondary amines, and lastly primary amines. 

In amines, the basicity increases as the number of alkyl groups attached to the nitrogen atom increases. This is because alkyl groups have an electron-donating effect, which enhances the availability of the lone pair of electrons on the nitrogen atom. Thus, it makes it more readily available to accept a proton and thus increasing the basicity of the amine. Tertiary amines are the most basic because they have three alkyl or aryl groups attached to the nitrogen.