Useful Stance numbers at Buchanan Bus Station:
Stance 4 - Stagecoach Express buses to Fife - X24, X27
Stance 6 - Stagecoach West Scotland X77 to Prestwick and Ayr
Stance 8 - Stagecoach West Scotland X36 for Dalry & Ardrossan
Stance 9 - Stagecoach West Scotland X74 to Dumfries
Stance 46 - First Glasgow 500 to Glasgow Airport
Stance 48 - Citylink AIR service to Edinburgh Airport
Stance 49 - Citylink 900 to Edinburgh Bus Station
Stance 50 - McGill's 901 and 906 Clyde Flyer to Largs
Stance 52 - Megabus M9 to Dundee and Aberdeen - and M11 to London
Stance 53 - ember E3 to Dundee - and Citylink 926 to Campbeltown - and National Express 182 to Carlisle and Birmingham - and National Express 590 to Carlisle and London
Stance 54 - Megabus M10 to Inverness
Stance 55 - Citylink 975 and 976 to Oban
Strathclyde Passenger Transport have a full list of routes and stances at: https://www.spt.co.uk/travel-with-spt/bus/bus-stations-travel-information/bus-stations/buchanan-bus-station-glasgow/
Remember that if the bus station is busy for whatever reason then buses may depart from nearby stances rather than their scheduled stances - keep your eyes and ears open for announcements and changes to electronic displays. Infrequent services such as those from Flixbus will fit in on whichever stances are free at the time...