[bcj]

Helmets will have different padding and overall shapes, as do riders heads.
What works well for one person will be completely unworkable for someone else.
You'll have to actually try on a lot of them to find one that works.
Pay particular attention to pressure points. You may find some awful annoyance after a couple hours.
The cheek pads may seem too tight when new. They will loosen up eventually.

Single piece leather suits are best for racing, but can be pain trying to peel off after a commute.
A colleague at work commuted with an Aerostitch single piece textile suit. They have a good reputation, but at $600 to $800 they can be a big chunk to swallow.

Look into two piece textile gear to get started. You can get better gear later if you decide to get more deeply involved.
The pants and jackets will come with zippers to connect them together, though you may have to get a compatible zip strip sewn in.
Each piece will have both zipper halves you can use the loose half on the incompatible other piece.

A 3/4 length jacket is better for colder weather than the shorter length sporty jackets.
Most will come along with zip in rain and insulation layers.

Textile gear should be thought of as single incident protection. If you dump and it gets damaged, replace it rather than re-use.