Is it advisable to level in a jack-of-all-trades, master of none kind of way? I'm only level 35 or so, and I've got my STR and DEX at 14, INT at 6, ATTUNE at 10, VIT at 12, etc.
Should I ignore certain categories as I go further? I want to cast basic spells, have high mobility/roll and be able to use bows as well as sword and board. Is it a mistake to pump souls into some of those things?
This is in regards to PvE, if you are going for PvP, I know nothing:
Honestly, I think its actually better to spread your stats out a little bit instead of being super focused. The reason being you get a good enough boost from most stats when only leveling them to 20. Then the diminishing returns kick in, and they become less and less useful. So what I generally advise is:
1. Boost VGR, VIT, END, and ADP to 20 - this gives you a good amount of health, equip load, stamina, and maneuverability
2. Pick two out of these four in terms of what damage/weapons/spells you want to use: STR, DEX, INT, and FTH
3. Boost ATN as needed to unlock the amount of spell slots you are comfortable with (I'm not sure of the exact level breaks for this)
Ultimately the biggest decision is part 2. A common build is focusing on STR and FTH. This allows you to be a good melee fighter as well as having access to some strong and cool miracles and even pyromancies work well. In this case, completely avoid INT and level DEX only as needed to equip what you want to equip. You can even fit in some bows/crossbows that scale with STR.
You can focus on STR & DEX as there are some cool weapons that require a nice chunk out of either, especially if you want to dual wield. This gives you better access to bow type ranged options, but you may need to avoid magic a little bit.
You can also go very magical with INT and FTH, but I'm not sure at all how to build those types of characters.
Ultimately though, it really all depends on where you want to stop your soul level. If you are only playing PvE, this becomes a non factor, and you can just continue to blow up your stats to whatever you want.
I'd say the only time to avoid being a "jack of all trades" is very early on. In the beginning, I think its better to start focusing on one thing (say, STR) to get some good assured damage of one type before moving around. Especially in terms of reaching equip requirements as soon as possible.
Hope that helps