Been to Israel a couple of times (on my own, not birthright).... one of my favourite "tricks" is to find a guided tour that is nearby, and just tag along at the back. (Don't get in front of any of the paying clients, that would be rude! But just close enough to hear the guide.) Then when the tour moves on you have time to go back and get a close look, and time to soak it in. Then when the next tour group arrives, still at this same spot.... listen in again. You will likely be amazed at how even a small change in emphasis can alter what you thought you understood about the that site. And sometimes one guide's interpretation can be very different from another's. Do this 3 or 4 times if you have the patience and time.
The whole point of this is: Everything in Israel is old, really really old, and historical sites are important to 3, 5, 7, current "groups" and were critical in the development of another dozen. The best way to "get" this is, imho, to either take a course (expensive and time consuming) or - listen to 2, 3, 4 different tour guides (for free) who are each bringing their own background filter to how they explain the significance of the site. To my mind, it's the layering of history in Israel that boggles the mind.
Note that Israelis of your age are among the most attractive I've ever seen - so hang out on the beach.
Israelis don't believe in "being quiet and polite" - it's the person who shouts the loudest that gets things done. At least this was true 25 years ago... but I don't think it's changed much.
The Jordan River; it ain't deep and it ain't wide.
You have to go to Masada. Go on your own, and hang out on top for a long time, tagging along on the groups. If you "get" Masada, you will start to "get" Israel. Or at least the young Israel of 60s and 70s.
Do not, under any circumstances, leave any luggage unattended for even a second. When I was there, I got to watch the bomb disposal unit blow somebody's underwear to smithereens at least once a week. They clear the area, bring up a robot with a shotgun, and blast the suspected bomb. It's almost always some tourist's backpack that had been left "for just a minute". Now with a giant blackened shotgun blast right through it. No apologies given.
It used to be that you could show up at a Kibbutz and volunteer. It's a great way to stay for an extended period of time for free. They used to even give you pocket money, so you had some money to tour the country on your day off.
Israel is small. It is really really really tiny small if you are used to North American/Australian distances. Just a little small if you are used to European distances. If an Israeli starts to tell you it's too far to get there easily.... make sure you get the actual distance before deciding whether to go.
Watch out for traffic. Assuming things have not changed much since I was there, you are more likely to die of a traffic accident than a war or a bombing. Much more likely. I was in a car there, as a passenger. We were 3rd in line, with the 1st vehicle going very slow (i.e. going the speed limit). The 2nd car found a gap in the oncoming traffic and started to pass. Not quickly enough for my driver, who slipped between the 1st and 2nd cars while the 2nd car was next to the lead car. When I checked my mirror to see if there were flying cars behind us, all I could see was the grill of the bus that had been tailgating us before this maneuver had started.
Luck.
