In general, a thief won't be much of a thief without snooping. Random stealing runs the risk of attempting to steal an insured or blessed item - which you can't. So you'll reveal with no chance of stealing the item. Also, grabbing a random item isn't nearly as fullfilling as hand picking the item you wish to steal.
I believe every thief is going to need stealing, snooping, hiding and stealth. From there you can choose other skills to suit your preference/playstyle. I prefer Ninjitsu, wrestling and magery.
Now you did mention stealing from the champ. While I haven't tried in a long time, I was under the impression that you couldn't steal from monsters anymore. Barracoon may be different since he starts off as a human. If you can, I can't imagine the champ will have the scrolls in his pack. Otherwise, you could get the champ up with a warrior, switch over to your thief and just steal all the scrolls with relatively little risk. (steal, run away, repeat). But if they do, please let me know!
As far as people shooting you as soon as you appear, get used to that. My primary method after stealing is to use invisibility charged jewelry. As a backup, I use the invis spell with protection on. As long as you can live the few seconds it takes to cast, you should be alright. Keep in mind, you can begin stealthing right away now, but you must hide at some point. Otherwise, once your spell wears off, you'll reveal. Or your invis jewelry will keep burning charges.
If you want any tips or lessons learned from my champ spawn stealing, let me know and I'll pass along the knowledge I've obtained over the years.
Origin Thief