Truck not firing like it should

My truck stalled at a friend's house with a no start.
Drove fine there but when I tried to start it wouldn't
turn over. Thought it was the battery because it
definitely needed jumping after a few cranks.
Came the next day with a brand new battery. Same
thing. No turnover. Took fuel filter off and blew it
clean then put back on and like magic, fired first
crank. On the way home I stopped and bought a
new fuel filter and replaced old one. Fired like new
and I was a happy Steven. I even fired it 1st try at 2
hour intervals.
Next morning go to start and same thing happens.
After about the 3rd crank she fires right up. At this
point I'm thinking spark plugs or wires. She's
almost to 100k so maybe it's about time. New
battery, fuel filter, plugs & wires later and she's still
firing 2nd or 3rd crank, sometimes 1st try. The
altenators about a year old but it's been squeaking
since I replaced the serpentine belt. Not bad at first
and good after I spray some belt conditioner in it. A
month ago the alternator started "whirling"
annoying the piss outta me.
Could my altenator be the 3 crank issue or is it fuel
related?