New To Gz250 ('07 W/104 miles)

[Water Warrior 2]

Welcome to the forum. Sounds like a wonderful deal on the bike.

Old hairy tires will hurt you. New hairy tires won't. Any tire over 5 years of age is a liability. Rubber gets dry, hard and slippery. Not a great combo for safe riding.
As the bike has been parked for years you should give it a complete lube job. Lube anything that should move.
Cables, sidestand, pivot points for brake lever, clutch lever, rear brake hardware etc.
Spray contact cleaner into all switch gear. As much as it may seem stupid.....................replace all the bulbs in the lighting system. Bulbs get dimmer with time even when not used.
Going over the bike with some TLC will introduce you to the workings of the bike and increase confidence overall and knowledge.