According to a recent article in Flex magazine the optimal dosage for caffeine should be around 3-6mg/kg of body weight.
At 180lbs you are looking at 246 to 492mg.
Start with about 100 – 200mg to access your tolerance when using caffeine pills.
Source Citation (MLA 7th Edition)
"Optimal caffeine dosing." Flex Sept. 2013: 90