Cufflinks are an absolute must for a morning coat ensemble because button cuffs would be too casual. Classic cufflink variations include platinum, pearl , ivory or gold. Whether you choose silver or gold, is up to you,just make sure you match it with the your other metal accessories, such as watch, rings etc. If you have a tasteful pair of colored stones, you may wear them, but otherwise I would stick to plain gold, silver, onyx or a pearl. Definitely avoid diamonds or other precious stones, as they are traditionally reserved for evening wear. The same used to be true for colored stone, though I think a bit of contrasting or matching color in your cufflinks gives your morning coat outfit an elegant touch. It does not really matter if you go with T-Bar, Snap or Chain cufflinks, there is no superior mechanism. Just wear what you like the most.
Sterling Silver, Mother of Pearl & Onyx Cufflinks with Tie Stick Pin
The shirt should have double cuffs with a turndown collar and either a double cuff or a single cuff for cufflinks with a detachable collar.In regards to sleeve length, I like to show a little bit of cuff, so the cuff links peak out just a bit at times.
Intricate Blue Enamel & Gold Cufflinks
To learn more about sleeve length, I recommend you read this guide.