Since the WLC 2100 does not support Link Aggregation (LAG) each interface must be associated to a physical port. The best way to support APs directly connected to the WLC is to assign both management and ap-manager interface to port 1. You can still configure different VLANs for the management and ap-manager interface, the directly attached APs will find both interfaces and join the controller.
It is important to be very patient and give the APs enough time to discover and join the controller.
The WLC 2100 ports support Auto-MDIX so you can use straight as well as cross-over cables to connect the APs to the controller. In the screenshots below you can see a WLC 2106 with both ap-manager and management interface assigned to port 1 but configured on different VLANs. Two APs are directly connected to the PoE ports of the WLC, one using a straight cable and one using a cross-over cable. A third AP joined the controller from a switch connected to the WLC.
Note: Whereas it is possible to connect the APs directly to the controller, I would recommend to connect the APs to a switch. This will allow you to get trained on many IOS commands that are required during the lab and are not configurable on the controller ports.