Honestly if you're just wanting to go lancer, don't worry too much about polearm wpf. If you want to use polearms on foot though too, then sure, but more points into polearm. Also, if you only really wanna use 1h from horseback or use it as a secondary skill, you could easily get away with 50-100 wpf, it's just not ideal. For a primary weapon I'd say 110+, though.
Just edited my post a bit too :O