I'm exactly the opposite. I'll almost always roll for non limited units, and only roll for limited units if they seem super OP. It's the only way to build a reasonably sized collection of units that can handle diverse content. If you only ever roll for limited units, then it's literally guaranteed that those are the only units you're ever going to have, since no other 5* are even in the pool on limited banners. That's too steep a price to pay for me, unless the unit is ridiculously good (granted, since they're limited, usually they are going to be ridiculously good)
Like I didn't get Lidica on this banner, but I did get Basar, who is honestly pretty bad, but a year from now (or whenever) when he's buffed, gets a specialty change, or for some other reason becomes important for something, I'll at least have him.
Well, its more about the pity rate than whether the unit is limited. Having a guarantee that your luck won't screw you too badly helps a lot, but I have to like the unit as well (I wouldn't have rolled for Violet, even if he was limited).
Non-limited units go into the pool, so I might get them later on during a daily summon. I might also get them when rolling on a non-limited banner (e.g Tamarinne), since rate-up can be a lie.
I'm not spending on the game, so the amount of bookmarks I have is limited. So I horde 605 BM to make sure I can get something from a banner, being lucky will just be a bonus. I really like Tama even before buffs but I didn't roll too much on her banner since I figured a limited banner was coming. Once I got Yuna, I tossed all the remaining bookmarks at Tama, since i figured there would be time to save more.
So why am I suppose to be farming wyvern stages and what am I suppose to be doing as a result of wyvern farming? I just hear about it but no one actually explains anything beyond how to build a team for it.
Others have already explained it, but basically you can toss a speed set on just about anyone and it would be pretty good. Speed gear drops from the 2nd Lab and Wyvern. Generally, you should do 2nd Lab until you can do Wyvern 8+, since Lab drops level 45 gear, and the chances of getting a significant upgrade (lvl70+) only starts at Wyvern 9. If I remember correctly, Wyvern 8 only drops level 41 rings & necklaces). If you craft, you can get the mats earlier, but crafting is expensive and subject to the same RNG.
Since they also drop Hit and Crit set gear, you can just run Spd/Crit on your dps, and Spd/Hit on your debuffers, which takes care of most of your gearing needs.