I'm enjoying this web game a lot
Glad to hear it.
Yes, it's quite good.
what are the guidelines for making my first little colony? Should I keep it in or out of my starting region? And should I send escorts with it (seems logical to do so to me)?
Depends on how cautious you want to be. If you blindly send an outpost ship to a system you can't see, the best case is that you colonize the base with no issue. But if you can't see it, it's possible that the base may already have been colonized since the scouting data was last updated. That can be inconvenient, especially if it's an 18+ hour trip. And worst case, you fly right into a hostile force and you lose the outpost ship and the 100 credits it cost you to build.
The safest option is to send an advance scout to the region so you can see it, and to be sitting at your computer watching when your outpost ship arrives. That way, if anything hostile shows up you can recall the outpost ship and it will return to its origination point.
But if the risk of losing a 100cr ship doesn't particularly bother you, sending it blind and unescorted is admittedly convenient.
Note though that the current colonization list is two days old, and as you've probably seen mentioned on the boards, many of those bases are no longer available. So it may be worthwhile to confirm your intended astro is still available before sending the outpost ship.
Is my starting region basically always scouted for me?
Regions you have bases or fleets in are visible to you. Systems that guildmates have bases or fleets in are visible to you.
does it annoy my fellow dwarves if I put a colony in one of their systems, or is better for us to spread out from each other?
It's generally appreciated, as there are reasons for players not to colonize a bunch of bases in the same system themselves, and having them colonized by you prevent anyone else from taking them. This reduces attacks of opportunity. For example, if someone hosile colonizes a base in the same system as one of yours, it's very easy for them to see your base, and even to keep a large fleet right next to it protected by their base defenses. It's easier to attack a target right next to you than to go looking for targets somewhere else.
By colonizing bases in the same system as your fellow dwarves, you reduce the chances that hostiles will do so, thus reduced the likelihood of your fellow dwarves being attacked.
It also makes it fast and easier to help liberate each others bases if occupied.