If you are trying to lose weight have less calories and add more cardio to your workouts, you mainly want to stay in a higher rep range lower weight if you want to try and lose fat.
If you want to gain muscle size get moderate weights and stay in the 8-12 rep range. Make sure to have 1-2 min rest in between each set and eat ALOT. If you are skinny then you are going to need to up your calories bit by bit everyday. Once you have the desired mass on your body then it should be time to cut down.
Just buy a dumbell set they are pretty cheap and really effective, i never go to the gym i just workout at home with dumbells and a gym set.
It really depents on you. If you want to be fit then go for more endurance exercises, if you want to be big and have more strength then go for hypertrophy, if you want just strength then train with very heavy weights. My diet is mainly calories and with my health problems i can eat lots of calories even if im cutting down so everyones different.
Also form is extremely important. Don't just get heavy weights and swing them up, i did that mistake and it literally did nothing, so remember have really good form and pick what you want to do. If you are going to bulk up then i don't think you should be worrying about abs right now.
Keep doing research and try go to a gym or buy equipment.
Best regards!!!1!1!!!12