Connecting switches together

I have L2 switches which will be daisy chained together (yes I know, daisy chaining isn't great, but anyway..) The L2 switches will then link to a L3 switch.

Both the L2 and L3 switches have x4 10GbE SFP+ ports.

Something like this?

+------+            +------+            +------+
|  L2  |SFP+----SFP+|  L2  |SFP+----SFP+|  L3  |SFP+-----Server with SFP+
+------+            +------+            |      |SFP+-----Server with SFP+
                                        |      |SFP+
                                        +------+

Would I be able to daisy chain the L2 switches together using the SFP+ port with an Ethernet cable?

If the switches are ethernet switches, then the only cables you can use are ethernet cables. Remember that ethernet runs on a variety of media, including UTP and fiber optic cable, so any cable used for ethernet is an ethernet cable.

Also I was going to link the L2 switches to the L3 switches via Fiber using the SFP+ ports. However in some cases, that maxes out the L3 switch, and I need at least 8 SFP+ on the L3 switch, so is this just a case of adding extra SFP+ modules to the L3 switch?

Based on your description, I do not see the need for eight SFP+ interfaces in the layer-3 switch. Whether or not you can add SFP+ interfaces to the switch depends on the switch model and if it has slots for more SFP+ interfaces.

Layer-3 switches are first layer-2 switches, but also have an internal routing module. Other than that, the switches are switches, and you can use the SFP+ as switch interfaces in either type.

I also have two different servers, one which have 10Gbe port and one with 10Gb port, would I be able to connect these to the L3 SFP+ via fiber?

That depends on the server hardware, which is off-topic here, but if the server NICs have slots for SFP+ interfaces, then there should be no problem.