Relative file path/folder (AppleScript)

How do I set a folder as a realtive path to where the script is running??  

is there any easy way like in unix, starting without / ?

or for example

"~/Desktop/"

"/users/<login>/desktop/"

seems that path to me is the only way...

is there an easy way to change posix paths to applescript??

I have this code:

tell application "Finder" to set templateFile to (container of (path to me) as string) & "Graficas FINAL ADQAT.ai"

with this error:

error "No se ha encontrado el archivo Macintosh HD:Users:Vibra:Desktop:Graficas FINAL ADQAT.ai." number -43 from "Macintosh HD:Users:Vibra:Desktop:Graficas FINAL ADQAT.ai"

the file is there how I change the filepath to be compatible with applescript??