Hi there, here are some suggestions I have:
1) I think monks are generally a good idea. Otherwise if you are specifically looking for something to pair with a casual outfit, I think you can also consider a pair of brown wingtips (rather than longwings), which may have some utility even in a slightly more formal setting.
Your friendly Swedish retailer @Skoaktiebolaget carries Carlos Santos which would probably fit your budget. You can check out this pair:
That would make a pretty good choice I think. It also has rubber soles that would be good for the wetter / colder months.
Alternatively, you can also consider this:
It's casual yes, but a pair of full brogue oxfords is pretty versatile and something you can consider since you don't have one yet.
Generally, rubber soles are preferable if there is a concern of wet weather. Leather soles, once they have become soaked and waterlogged, may tend to give rise to mould growth even after they are dry, and especially if your environment is humid.
2) A lot of the suedes out there on RTW shoes are actually split suedes. In a sense, these are leftovers from hides after the best part of the leather (with the grain) has been split away. Thus, split suede is usually thinner. Most folks use a nano protector spray prior to first wear, and once every few wears, which may confer a degree of water resistance to it.
Generally I prefer calf for wet weather shoes. If torrential rain or very wet conditions are a concern, SkoaB also sells Burgol Piz that you can use on your shoes. This is really helpful.
Scotch grain, while giving a unique, country, rugged appearance to your shoes, are generally not much more water resistant than regular calf. The grain pattern is embossed.
3) Probably a very dressy black derby with 2 or maximum 3 eyelets in a formal looking, sleek last. Black chelsea boots are also a classic, "can't go wrong" pair.
4) This is a question with numerous aspects to be addressed. I'll only give a very short version of what's MY opinion, and many others might not agree with me. What I feel is that price and quality have almost nothing to do with each other. Just because a shoe is thrice as costly, doesn't mean it's thrice as good.
IMO, the most significant (but not the only) difference that I would look for, would be a handwelted shoe. Construction method might not be the only indicator of shoe quality, but to me, it's the most important. A handwelted pair of shoes is unequivocally better constructed than a GYW pair. If put to the test, yes, they would be more durable. Quality of materials would also be important to me. A shoe maker who cuts his uppers using only the best part and thus getting maybe 1 or 2 pairs at most per hide would be better than a maker who utilises the whole hide and cuts for economy. Full leather, veg tanned insoles and outsoles are also something I look for.
The discussions on this topic are endless, but you need to know exactly goes into your pair of shoes, know the construction methods, before you can really appreciate the differences.
5) This really depends, on the quality of the outsoles, how often you wear them, the terrain you bring it through, your gait..... etc.
By and large, the toe area tends to wear down quicker than the rest of the outsole, and once it starts to wear so thin that the welt area is nearly compromised, you'll need a resole.
Also, I find that rubber soles last significantly longer than leather.
Edited by ThunderMarch - 8/1/16 at 8:35pm