All just personal opinion here...as I've only been through this once and with a kid who decided to play college ball really late, but these were pieces of advice I received.
Honestly, I think social media is a great tool... for a good laugh. I still don't think you can beat a directed email with a 30 second video of your swing, your pitches or your fielding mechanics, sent during non-blackout period, to a specific list of coaches/schools you want to playfor/attend. That way you can stay in control of what is seen and by whom. And that target list should include schools at all levels.
Coaches are busy, don't send them 4 innings of game footage. 30 seconds per skill is more than enough for a coach to determine project-ability, fielding skills, and if you can barrel up a ball, to spark interest and potential visit for an in person look-see.
And like others have said, nobody, especially coaches, care one iota about High School, travel or any other stats. Maybe, maybe... a stat line saying you went 3-4 against the #4 pitcher in the country, or shut down a team with x,y and z D1 P5 commits/pro prospects ...but otherwise there is no comparison that would mean anything to a coach like stats mean in MLB.
I had a hitting coach tell my son if someone can't hit .400+ in HS ball (d1 level), they basically can't hit. So sending hitting stats is probably a "who cares" at best and a "warning sign" at worst.
Advocacy by respected coaches, trainers, etc that can provide insight into your ability, work ethic and personality is much more effective.
My take on when to start, For 90% of people it starts summer after sophomore year of high school. kids who are getting recruited before that are the 1%'ers.