Eighteen inches long is ideal. A longer trace than that can cause problems, especially when casting. A shorter one could mean that a bite-off is more likely. Don't listen to the advice from the occasional piker who suggests that you don't need a trace, you do. There are those that consider braids are immune to a pike's bite, rubbish.
Braids are neither immune to bites, nor abrasion.
There is no excuse for not using one. Almost ready, you need some lures. The choice is mind-boggling. The right dealer can give sound advice but such dealers are few and far between, most being more interested in carp, carp, carp and yet more carp. For myself, if I could only have a few lures, then I would plump for spoons.