Can I enchant a Light Spiked Steel Shield with +1 for AC and ACP, and another +1 for Attack and Damage Rolls?
What would the price be, and how would that be calculated? Two separate +1’s or would they combine to a +2?
You simply treat both parts of the shield as separate items, then add their costs together.
For the Defensive part, +1 shields are priced at 1,000 gp, plus the costs of the mundane shield, plus the costs of the masterwork quality of the same shield (+150 gp). So, for instance, a +1 heavy steel shield would cost you 1170 gp.
For the Offensive part, you add Shield Spikes to your shield and work on that as a weapon, effectively enchanting a separate item. +1 magic weapons are priced at 2,000 gp, plus the mundane version of that weapon, plus the costs of the masterwork version of that weapon (+300 gp). So, a +1 shield spikes would cost you 2,310 gp.
If you add both together, the market price of such item would be 3,480 gp. Since only the enchantments can be discounted when crafting magic weapons or armors, the costs to enchant one by yourself would be 480 gp on mundane materials, plus 1500 for the enchantments. For a total of 1,980 gp.
Even the mundane parts could be crafted, but that would take much longer as using the Craft skill is much slower than using magic.
Yes a shield can be enchanted for both defense and offense, but it can get a little weird. For this to work, the shield spike is required. Both the shield and spike must be masterwork (yes both must be paid). Then you can enchant them as you wish, the spike as a weapon and the shield as armor.
So in your case pricing would work out to shield + shield masterwork + shield material + armor enhancement bonuses + spike + spike masterwork + spike material + spike weapon enhancement bonuses.
What I did with a character was a suit of armor which had armor spikes, and then gave them the defending bonus since I generally wasn't going to be using it for attack. There is also guardian if you want that to be applied to saves instead.
The Pathfinder PRD states:
An enhancement bonus on a spiked shield does not improve the effectiveness of a shield bash made with it, but a spiked shield can be made into a magic weapon in its own right.
While not terrifically well worded, the first enhancement refers to the shield being enhanced as a shield (this being a part of the armor section of the PRD). The spiked part of the shield can then be separately enchanted "in its own right", giving +1 to the AC as part of the shield enchantment, and +1 attack and damage as part of the spike enchantment.
As they're separate enchantments, they are tracked separately — adding up the levels of enchantments is only for one specific set of enchantments to either an armor item or a weapon.
Yes, you can do this. The spike and the shield should be enchanted separately. For example, for a light spiked steel shield which was +1 as a weapon and +1 as an armor, you would pay:
19gp (light spiked steel shield for medium character)
150gp (the shield is masterwork armor)
300gp (the spike is a masterwork weapon)
1000gp (+1 armor enchantment)
2000gp (+1 weapon enchantment)