Healthy hair is always the best hair to work on. Any colour will come out perfectly if you've taken care of your hair prior to a colour service. Healthier hair also shows the least damage once the colour service is completed.
Bleaching your hair at home is only safe on virgin hair. Although strongly not recommended, many clients try to cut costs by doing it at home despite the dangers. If you've had previous colour on your hair, it is not advised to do it at home because monitoring the damage isn't always possible and can lead to roughened cuticles scales on the hair stand, brittleness and excessive breakage. Seek the help of a professional if its not virgin hair.
Bleach is best done on hair that has not been shampooed in 24hrs for the most effective results. The natural oils of your hair will help perfect both your hair and scalp. If hair has not been shampooed in a longer period, 1 light wash will help to remove some of the debris to make the colour results more successful. Hair that is already brittle or broken should not be bleached until restructuring treatments have been applied to strengthen and repair the hair prior to a bleaching service. Treatments such as Olaplex, Chromoplex and Biolustre are great to help prevent breakage during services as well as repairing brittle hair immediately after a bleaching service.
Toners may seem like a waste of money if you're trying to save money, but it is vital to achieving your desired colour. Lots of undertones remain even after a successful bleaching service and can deter you from continuing on your colour path. Toners are there to help keep those tones under control without the continuous use of violet shampoo that can leave your hair hard. The use of violet shampoos are protein based so continuous use will harden the hair and increase the chance of breakage over time. It should be used with a moisturizing mask/treatment and should only be used every 2 weeks as opposed to daily use.
Always use heat protection on bleached hair because its naturally sensitive and always use a mask/treatment post colour service to restore some of the lost nutrients. Ultimately the best would be to ask a proffessional. it will save you time and money.