You’re going to get a lot of conflicting advice. People have very strong preferences and opinions about breeches. Also, different brands fit differently. And your body shape will definitely affect how certain breeches fit and feel. Equine Couture, for example, tends to fit people who are thin and not “hippy.” Ariat fits people like me: the classic pear shape.
There’s also a strong sense of fashion in the H/J world–that’s not bad, but people will try to persuade you that tacit trends are in fact rules. Tailored Sportsman breeches, for example, are beautiful, but you do not need to spend that kind of money to get a nice pair of show-worthy breeches. I will try to address your questions, but remember, no one has all the answers.
side or front zip? Either is fine. Side-zip is more traditional, but front-zip is perfectly appropriate if you like it. Some complain that the front-zip make a tummy bulge. Personally, I prefer side zip for shows, but again, that’s optional.
2, 3. ribbed fabric: This is exactly what it sounds like. Think of corduroy. Ribbed breeches are stretchy and comfortable. The Tuffrider ribbed breeches have legions of fans (including moi). However, most on this board would not wear them at shows; they are generally considered more of a “schooling breech.” However, since you are wearing a helmet cover, I assume you are showing at a small, local show, so beige ribbed breeches would probably be OK.
low rise or mid (regular) rise? You did not ask about this, but you need to. The “rise” indicates how high up on the waist the breeches will hit you. Low-rise breeches are extremely popular, and most riders today will not wear anything else. However, mid-rise breeches are perfectly correct, and have the advantage of helping to keep your shirt tucked in and looking neater when your coattails flap up as you ride. Even with the “low” rise, brands vary. Some low is very low, others are more moderate. Try them on.
Other confusing features: You will see some with a wide waistband (more trendy now) and others with narrow belt loops (not as stylish, but perfectly correct). It doesn’t matter which you choose, as long as you have something with an actual zipper and belt loops. Don’t buy the “pull-on” kind to show in. The “euroseat” is another trendy feature. This is a seam that outlines your butt. Again, it’s optional. Some will tell you it’s a “must-have” feature; others of us don’t care to have our least attractive body part outlined.
I do not recommend the Cotton Naturals. They are well made, but they do cling and show every bump. I had a pair of these and finally got rid of them for that reason.
There are lots of good choices for you, and people in this thread will recommend their favorites.
Since you are in Texas, I recommend that you consider the Devon-aire Versailles breech. The fabric is smooth and satiny but thin. They look nice and are inexpensive. I live in south Georgia and wear nothing else in the summer. They are not breeches for an A show, but it sounds as if you don’t need those.