In my opinion, if your overnight trips will be infrequent, it's not worth it to buy more expensive gear. This means your pack for the overnight trips will probably need to be around 50-60 liters. You may carry more weight than others, but since it's just one day, you won't be loaded down with a lot of food.

My son does just fine with a schoolbag for day hikes. I see all kinds of little bags on the trail and most are more expensive than they need to be. Last weekend I saw a guy with an old pack with a beautifully finished wooden frame. That was the classiest one I've seen. In my opinion, spending a lot of money to save a pound or two on a day pack isn't worth it.

I find suspension isn't so important for dayhikes as the pack is light and I never notice the pack. What may be more important is how it holds your photography gear.

Hiking in jeans and sneakers is fine if you can keep dry. For cheap pants, I prefer cargo pants from WalMart for about $14 as they have more pockets. They are cotton, but my fallback position is to wear my rainpants. If jeans are more comfortable, just carry a pair of synthetic pants in your pack for wet days.

Keep in mind Glenn and I are on opposite sides of the gear thing. Glenn seems to enjoy getting a lot of new gear. I've become almost evangelically opposed to this approach. I prefer to use my gear to extinction. If I have time to drive to REI to look at new gear, I have time to get one more trip out of the old gear I have.

I've also become more minimalist as I get more experience. It's just walking and sleeping on the ground for a night.