1996 Nissan Truck starting

When I turn the key the truck either cranks right up or it makes an electrical sounding clicking noise if it doesnt crank within about 4 or 5 tries it usually drains the battery both the battery and spark plugs are under 6 months old is this the starter or the ignition switch or something entirly different. There is a light tappin sound when I accelerate like there isnt any oil in it but it hasnt got a leak and it is got plenty in it. Any suggestions will be greatly appreciated id like to save myself the large bill from any diagnostics test a mechanic will want to run