40 bulb chandelier wiring project - Does dimmer affect amps?
For North American AC wiring, #14 wire is used on 15 Amp circuits, and #12 for 20 Amp.  You will need #12 wire, and a 20 Amp breaker to feed your chandelier.  If you could break the chandelier lights into two groups, you could use two 15 Amp circuits, and would have an easier time finding dimmers to control it.

A dimmer will reduce the effective current when the lights are dimmed, but I think the Electrical Code will require the breaker and wiring to be suitable for the maximum (full brightness) load.