[FishingForLife]

Welcome friend, to the "where did my money go" hobby. If your just starting out, Once you hit the water, it can be a bit intimidating.
For your fly size, it all really depends on the fish. I've seen a hatch of Size 16 BWO's, and all the fish want are large streamers. Vice Versa.
My opinion is, once you get near the river bank, kick over some rocks, look in the air, and on the water surface. If you see any sort of critters, grab your fly box and look for the closest thing to it. Even if you don't believe that's what it's suppose to imitate, if it looks close to it, use it.
For the flies, as a beginner, I'd suggest nymphing or chucking buggers. It's my opinion, that those will give you a better chance at success.
For Nymphs, I like; Bead Head Pheasant Tails [12-16] / Bead Head Prince Nymphs [12-16]/ Hare's Ear Nymphs (Grey & Green)[12-16] / Copper Johns [12-16]
For Streamers, I lean towards; Micro Leeches (Black-Green-Purple) [10-14] / Woolly Buggers (Black & Green & Purple & Maroon)[8-12] / Bow River Buggers [4-10] / Muddler Minnows [6-12]

If you want to try Dry Flies, there's no one stopping you. However, I would wait until you get the casting down pat, or see a multitude of rising fish, atleast, if you want relative success.

Also keep in mind, with the nymphs, sometimes the fish aren't big fans of the Bead Heads, they get moody, so feel free to go with the regular versions as well. I just like the bead because it helps it to get down a bit quicker.

For rods, I enjoy my 9'6" 6WT TFO. I did recently purchase the same rod in a 4WT, But haven't worked too much with it yet, so can't say much.
Lines, I'd recommend the Rio Gold WF6W. It can be a tad pricey, but you can beat the snot out of that line, and it'll keep performing.
Hope this helps! Tight lines buddy!