Congrats on your first shave!

First off, you should not expect nice shaves for a little while, and you should not try xtg or atg for awhile either.

You did good beard prep, and if it's Mitchell's Wool Fat you are using, check out this thread for lathering tips. It is a little tricky to get it to lather up nice, but once you can do it boy oh boy do you ever get a great lather!

As far as the shaves go, getting a good shave with a straight is dependent on more than just a sharp razor, but good technique as well. Technique is only developed with time and experience, and right now your time and experience is exactly one shave. Read the wiki, watch videos, and while shaving put all your focus on executing proper technique. I focus on keeping the skin tight, the touch light, and my angles right. Within a dozen shaves you should be getting really nice shaves. If you are getting irritation, the most common culprits for beginners are using too much pressure and too big of an angle (which you caught yourself doing). Another nice way to judge your angle is to use spine widths. 2 spine widths off the face is about 30 degrees. Its often easier to use this method than trying to judge angles in the mirror.

Your face need time to adjust to straights as well, which is why its recommended that beginners only do wtg for awhile. In addition, as you go from wtg to xtg to atg, technique becomes more and more important, so even if you are getting decent wtg shaves, you may not have developed your technique enough to get nice xtg or atg shaves.

Good luck with your future shaves! I look forward to hearing your progress.