Flip flops, walking shoes, shorts, jeans (in winter) and T-shirts are standard attire. Bring a dressier outfit just in case you want to experience the fine dining scene or have a romantic evening.
Toiletries and Medical Supplies: Sunscreen, mosquito repellant if you plan to explore wooded or wetland areas on a hot day
Photo Equipment: Certainly bring a camera! Jacksonville abounds in beautiful and scenic photo opportunities. Just look at the various tips I have written.
Luggage and bags:
I always favor a Large Rucksack with any traveling i do, as you will have to do a lot of changing of transport etc to get to where you going. Have found that large suitcases are just to awkward.
Clothing/Shoes/Weather Gear: Light weight, it awlays seems to be very hot here no matter what time of year im there. However it is alway worth taking a light poncho or rain proof jacket as showers are very frequent in the summer and autum months
Toiletries and Medical Supplies: Sun Block Sun Block Sun Block, the sun is very powerfull and even in the early morning will burn if exposed for even the shortest period of time. ( yes thats through experince )
Camping/Beach/Outdoor Gear: Lots of places to camp ( Hanna Park prob the best ) so a light tent would be worth packing, room permitting. However are very cheep from army surplus stores.
Miscellaneous: Fishing Kit, if you love to fish take your gear, as you will never be more than a mile from some prime spots, both Fresh and salt water.