I've just been using some bass poppers in assorted colors. Went to Bass Pro and didn't know what to buy.
Also, for LMB and sandbass, can I just continue to use 6# mono/floro tied directly from fly line to fly?
If using a fly that sinks, do I need an indicator or cork?
Lastly, whats a good place to buy?
I think you can cover >90% of freshwater situations you'll find in TX with Poppers, Clouser minnows, and woolly buggers.
For Clousers, get a mix of dumbbell and bead chain eyes, in sizes 2/0 down to 6. White/chart is my number one color, then olive/white, red/white, and one darker scheme. For buggers get a mix of unweighted, bead head, and cone head in sizes 4-8. Olive is my number one color, but white, chartreuse, and black are also good colors to have. These are both excellent flies for sand bass. Hit any local shop, they'll have those flies and will help you pick out a good selection. I would start with those, then supplement with local favorites and any flies you think are interesting.
For fishing sand bass: yes you can fish a straight piece of mono/fluoro off the flyline for the streamers (Buggers and Clousers are both streamers). A 7.5ft 2x or 3x tapered leader is a more expensive way that will work a little better, in my opinion. I do both, depending on how lazy and cheap I'm feeling that day.
You can use an indicator with either of those flies, depending on the situation. It will make casting harder, so I generally don't unless it's necessary. Keep a somewhat tight line to the fly and you'll feel the fish take the fly most of the time.
Look for any fly shop in your area, they'll be happy to help you out and answer any questions.