Captain obvious sneaking in, but There is tons of legit way to exercise, not just lifting weight in the gym, you can look for Volley-ball, Rock-dancing, or karate-class all of that is a legit way to exercise, which may even be cheaper and more fun than going to a gym.
Regarding your other points
-
Get a T-shirt and either a short or a pair of legging, to start-with you don't need any of these high-end expensive fabric (Which may help if you plan to climb an alpine summit or run a marathon, but not to lift some weight casually). Total cost should be in the 10-15 EUR range (It sucks to live in a world where clothing is built by slave-like-labour).
-
Most gym would include a couple of coached session as part of their beginner package. But a typical program would be like warm-up on a threadmill/eliptical then a bunch of strength exercise either on machine or free weight, and 10 minutes of cool-down with stretching, you can modulate duration/intensity depending on your goals.
-
You can do a lot at home with body weight. However, being in the Gym sometimes helps as you are in a dedicated place with a dedicated time-slot. ideally choose a place either near your home, or on your commute, if not you'll never go there
Et soyons fou, je fais un X-post sur !rpg@ttrpg.network ça fera un peu de contenu là bas aussi