Where in Glasgow?
AFAIK there is no bus service direct from Glasgow to Ed Airport.
If you are Glasgow city centre then Train to Edinburgh then tram (or Bus). to airport. if it is after 20th March - beware of engineering work.
OR
Get the CityLink bus service to Near the airport and "walk" the last bit. (You can probably get off the coach and get on a local bus/tram somewhere convenient).
If it is Glasgow Airport you will first need to get a bus from GLA to city centre.
If time is really of the essence, and money is no object then a taxi will cost about £70.