Buy some floss and floss in between your teeth every day, preferably twice a day. The gums
will bleed, but with continued flossing, the gums
will get healthier and much stronger.
Find a dentistry college near you. They are always look for volunteers to train on and are supervised. I do not know if they charge or if the work is done for free, but enquire. This will be your cheapest option.
Don't drink fruit juices and sugary drinks, they will cause more damage to your teeth.