I have a Tartan 27 that I keep at Watergate. Watergate does have some floating slips, but they are hard to get into.
The best launch point is under the kemah bridge on the North side. The south side is shallow and parking sucks because of the adjacent "boardwalk" You'll see the boardwalk when you enter/exit clear lake.
The "channel" from the ramp to the kemah/clear creek cut (main channel) is more like a ditch. It's very shallow so watch your tides. I had a C-22 for a while and used to use the ramp. I think you have 4' of water all the way and 6' in places. Of particular note there is a restaurant at the end of the ramp channel under the bridge, it's called outriggers. If the tide is going out there is usually a strong current there and you can get pushed up against their floating docks.
Best place for fuel is "3 Amigos".
Clear Lake is pretty shallow and you need to have someone basically point out where you can and can't sail. I'd highly recommend that you have a towing membership with TowBoat US or SeaTow (both have operations here). I refer to it as an investment not as insurance. lol.
As far as places to go, there are lots of neat things. Redfish island is a popular cruising destination. It's about an hour to motor sail to and is approximately 5.5nm from the boardwalk.
When using the clear creek channel don't leave the channel til you pass the second marker. I highly advise studying a galveston bay chart.
Redfish is a manmade island and you can anchor there and enjoy yourself. It's a great day-sail destination.
Galveston is about a 4 to 5 hour trip. There are 3 marinas there. Offats bayou is a great anchorage from what I hear. Be sure to check the charts before you go in or you will run aground. There is a area of 1 and 2 foot water in offats near the channel in the anchorage area.
Galveston Yacht Basin is a great transient destination. Clean showers, friendly fuel dock. They charge $5 for pumpout. Most marinas in Kemah offer pumpout for free to residents.
There are some things on the east bay that are worth visiting. A local cruising organization that I can't remember the name of has great writeups on the various destinations.
Most of the bay is 8 to 12 feet deep. Watchout for crab pots (marked by white foam bouys) and stay clear of the commercial ships in the Houston Ship Channel. There is a lot of space to sail, the weather is reasonable, and you can relax and enjoy Texas.
One other note, storms are very common. I got caught in one Saturday. I usually toss the hook and wait out the storm. They typically pass on by in 20 to 30 minutes. If you do plan to be near the ship channel make sure you have a functional VHF or two. I have a fixed and a handheld. Makes for a much safer trip when you can hail the commercial traffic and ask where it is going so you can stay out of it's way. The tows (tug traffic) looks deceptively slow but is normally cruising along at 15kts or more! Bolivar Roads (right off Galveston Island) is a very very busy intersection.
Again, welcome, enjoy, and be safe!
Hotpuppy Too, Tartan 27 - Hull #71 - 1964
Houston, Texas (Kemah)