I am 32 and got into Technic just half a year ago
I started with 8043. It is a really nice model and I like it a lot. It is smaller (less parts) than 8258 (which I do not have), BUT it has remotely controlled gearbox! And the B-model is great too - not as complicated as the excavator, but more fun to play.
I think you can pass on 8053 for now - it will be less fun if you do not buy a motor.
The backhoe (8069) is a great model. I think it is more fun than 8053 in spite of being significantly smaller. I really, really enjoyed it. For its size it's packed with functions.