The routes are all pretty short – you could ride all of them in two or three hours.
Basically there are two “zones” split by the access fire-road. To the north you have the lower red and the orange free-ride trails. To the south are the upper red and black routes.
Upper red and black share a common start but split near the top (brilliant viewpoint). They converge again near the bottom, so to ride both you’d need to climb the access road twice.
Lower red is a lovely route in its own right and joins the lower half of the orange route to take you back to the start.
My usual day at Laggan is upper red, black then a lap or two of lower red/orange.
Black is pretty technical (depending on what you’re used to)