A few tips.
Starting a company is a big project, if this is something you're serious about doing that is awesome!
Start going into shops and looking at all of the different types of clothing, you need to find a way to differentiate your company.
Talk to clothing buyers at shops, they are your customers, ask them what works and what they like.
Then talk to the people that will be using the gear, this is a great forum for doing so.
Make some friends at a fashion design school, they'll help you source materials, and make up your first samples.
Once you have samples, get your intended end customer to wear it and use it, what works what doesn't; fit, pockets etc..
Everything listed above is the easy stuff, now it starts to get hard..
I don't know your financial situation but your going to need a lot of money, over a million dollars for sure, sourcing materials, manufacturing, marketing, website, staff, travel, trade shows etc...
Good Luck, any questions advice shoot me an email.
- George