The bike uses standard 10w-40. You can also use Rotella 15w-40 as well, many people (including me) swear by it.
Do not use any 'high mileage' oil with added stuff. Base 10w-40 dino oil, or if you want to send $50 on an oil change you can go with the synth motorcycle oils (Mobile 1 RT, etc - not really suggested for our lower performance engine)- 3.25-3.5qts to fill her up - watch the sight glass and take your time (center stand).
Spark plugs are in my signature - go for the iridiums like I have. Makes a world of difference.
Look into replacing the battery with an AGM style if it has a standard wet cell.
1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Rebuilt Forks w/ Progressive Springs
VN750.com Grill Cover
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R
1990 Kawasaki Vulcan 750
1998 Honda VFR800 FI
2014 Honda VFR800F
1989 Pontiac Firebird Formula 350