@ArielLeslie offered some good advice. Body-weight, especially for beginners is great. But, it’s pretty boring, IMO. If you can get to a gym, you can focus on the machines, as they don’t require any special form, they lock your body in place for you, greatly minimizing the risk of injury.
However, if you stick to weight that isn’t too heavy for you, and practice your form, you shouldn’t injure yourself. Most of the injuries I’ve seen are from people that are trying to lift an excessive amount of weight. It’ll be their first day, they’ll load up the bar on the chest-press, and get stuck underneath it, haha. Also, those are the most common areas of injury: the chest-press, or squat rack. You don’t need to use them at all.
When you learn how to code, you start with variables and if statements, you don’t try to build an entire application. Likewise with lifting, you start with your form, get a feel for the weights, etc.
I would hold off on a trainer and see what your options are first. I’ve never used one, and I’ve been sponsored by a supplement company. But I have an older brother who’s been doing this for years, he basically trained me. i recommend to look for a friend or family member first. If not, a lot of gyms offer free 1-day training sessions. And again, if that’s not possible, and you can’t get a trainer, focus on videos. It’s not difficult to get proper form down for most exercises.
I started watching this guy about 10 years ago: https://www.youtube.com/user/scooby1961
Scooby places a major emphasis on injury prevention, home-workouts, proper eating, and he’s no-bullshit(he’s not going to tell you to take 50 different supplements, or any supplements at all). I recommend you to start here as well. He also has a website: http://scoobysworkshop.com/
Ok, I’m passionate about this, sorry for rambling. But, just remember, you don’t need to strive for a bodybuilder physique. Just focus on the movements, and improving yourself. The high feeling you get after a workout is pure tranquility, nothing beats it.