I guess we are somehow on the same level in regard of promises.
But in regard of traditional five or eight presepts, I guess our normal enviroment and livestile is not fit. They are also broadly abserved like Sunday Christians do it, in the countries where the eight precept day is a normal celerbrated day. Nice to be part of a community and give them also some feeling of doing something good. To observe one very good is much better from my view as to addopt traditional usuals.
Step by step but honestly is always good. For example, as long as I can remember, I just focused on that what is called abstaining from lying (everything else seems to be completely normal and out of the need or any special observation. Stealing, sexual misconduct, killing, drugs things which are logical and no base for worries normaly) and anything else came its way. But especially abstaining from endless eating with all our sense is very nessesary to get more intouch with the roots greed, hatred and illusion in our self. We might not see how greedy we are, we would be even so much distracted from the pleasure we gain out of it, that we would feel secure and use the Buddhas technics just as an additional pleasure pool.
If somebody is able to observe 8 precepts its something that is not usual and a bliss, who ever is able to do that will have great benefit from it. I guess it is good to give them some support to have the feeling that they are not alone.
Nobody ever had suffered in addition because he had started to observe precepts. It might be that it seems that things run more worse, but actually its not caused by virtue at all.
Just that! *smile*
BUT! it is important to become a real Buddhist first. Like Punna did: Nate sante baram sokham _()_