Why do you use a wicking tee and running shorts for your distance running? Why not use a cotton tee and cargo shorts? Do you use running shoes or Air Jordans? Cycling specific clothing has been developed because it can improve the experience and increase comfort. Having said that, wear what you want...if you find that you develop sores or have a lot of chafing then look into cycling specific shorts. If you don't like the tight lycra thing, there are mountain biking shorts that look like regular shorts but have a sewn in pad.

Regarding clipless...I rode with straps for a long time but I had very stiff shoes. As stated above, clipless has evolved because it's the most efficient way to transfer power to the pedals. It all depends on what you're trying to accomplish with your cycling.

Since you're new to the sport, please make sure you carry the stuff you need for doing flat repairs and minor adjustments. You don't need a saddle bag to carry things but if you're not wearing a jersey with pockets, you'll have trouble finding places to keep the essentials: Pump (either mounted on the frame or CO2), patch kit, spare tube, multi-tool, tire lever(s). Then make sure you know how to patch or replace a tube out on the road.