Terminal blocks and crimps are designed to used with bare wire, or without being tinned Please check the wire sizes that the terminal blocks and crimps are rated. This will ensure the greatest life for the connections.
If you use too small of a wire in a large crimp, the connection will be poor and may pull out of connector. Also, if you plan on taking wires in and out of a terminal block, then i would tin the wires. This will reduce problems with the wire fraying.