For safety equipment you can not have to much.
I do most of my boating in the ocean 10 to 70 miles off shore when it comes to getting someones attention can make the difference of spending a few bucks and getting help or causing alot of anxous hours for yourself and your family on shore
I have a flare kit like these https://www.westmarine.com/buy/orion...50?recordNum=6
with extra 12 ga shells...mostly ones I purchased new ones to replace these because they were over their expiration date. They still work well, just the coast guard or marine police will not accept flares that are expired.
IF you are going to mail order a flare kit check the shipping, they ship as hazardous material due to the flares and shipping can cost almost as much as the kits.
Also have a good VHF radio......you will lose cell service once you are around 10 miles from land.
I have 2 VHFs and have them synced to my GPS/plotter. If I need to send a SOS or hit the emergency switch it automatically sends the message along with my co-ordinance to any boat or plane in the area.
I also have a EPIRB to ensure if something happens quickly help will be on the way.
If I have my grand kids out fishing with me I have shown them all if I fell out of the boat or got sick they can flip a switch and the beeper goes off....ACR GlobalFix iPRO 406 MHz EPIRB w/ Internal GPS
Last thing is don't skimp on life jackets. Kent Commercial Type I life Jacket are around 60 bucks each but will roll an unconscious person onto their back in the water. The Kents also have reflective markings to make it easier to see in low light and I have a whistle tied to all of mine.
I have 3 of the inflatable jackets but they are not good for kids, people that are not able to keep awake and are difficult to put on in the water.
Weather can kick up in very short order and when you take people out on your boat you are responsible for providing more than just a good time.
The items above will last several seasons if taken care of properly
Buy what you can afford, when you can, again quality equipment taken care of will last many seasons.....good luck