It is not necessary to believe anything. Personal identity, religion, class or lack thereof is irrelevant. A Christian, Muslim, Jew, Atheist or any human being can practice in accordance with Buddhist methodology. The principle of 'dhamma' applies equally because nature's way is the same for everyone.
There is an ontological structure that integrates 3 parts: 1) you hear the teaching and know what it says; 2) you analyse what is said and understand it intellectually; 3) You investigate for yourself to find out the way in which it is true.
Nirvana is 'the final goal', so one must at least entertain the possibility of an ultimate truth, and the lesser reality of universal truth. The latter is easy. Death is universally true. The inevitable implies universality.
One aspect of practice is the contemplation of age, death and decay. When we see a dead body, a rotting body, be it human or animal, we know empirically that is the nature of all bodies, including mine. That's an example of universal truth - it's nature's way (dhamma)
Proir to practice there are two commitments: a vow to morality and refuge in the three jewels (triple gem). Superficially, morality entails 5 precepts. Don't steal, kill, get intoxicated. lie - pretty standard stuff. At a more profound level, morality pertains to will and ones ability to discern between good and ill-will. At first, obedience to rote assists without discerning, but through the third ontological principle, you grow to understand the nature of your own will.
The first refuge is refuge in the Buddha (the enlightenment within ones self). The second refuge is in dhamma (universal truth/nature's way) and the third is in the sangha (your teachers or spiritual community). The first two refuges are easy, though the first may entail a leap of faith, but the third is personal trust and it is prudent to be extremely discerning in that regard.
By committing to morality, one is motivated by what is 'right' rather than what is desired.
By taking refuge, one is surrendering to inevitable natural processes, having faith in one's own 'enlightened being', and enabling affection and giving and receiving service with regard to others.
The philosophy is not understood in the same way as Western philosophy is. The first two elements, hearing and understanding it intellectually are the same, but the third element of insight is that lightbulb moment of insight when one realises something irrefutable and goes, 'Ah, I see" (the way in which it is true).
This brings us to the 4 pillars: Body, sensation, mind, thought. Body and mind categorise empirical knowledge about a body such as bodies age, die and decay, for example. Sensation and thought categorise subjective knowledge such as 'this is a long breath' or 'this is what it's like'.
With the above theoretical basis, preliminary practice can be undertaken by feeling the sensation of your breathing. The process of meditation will reveal 4 basic truths 'This is suffering', 'This is how I cause suffering', 'Suffering is not inevitable' and 'This is the way to end suffering'. At first you will notice frustration, boredom, aversion to discomfort and other reactive tendencies and know, 'This is suffering'. Next you will realise that adverse and craven reactivity directly causes suffering, and it follows that ceasing to react thus brings about its cessation.
It becomes intricately involved with the moral dimension as you see how reactivity incites will and positions 'me' as the affected who thereby exerts volition to effect the world. That cause and effect is the cycle of karma. Karma is the incitement of volition and volition is the cause of outcomes. Since we react to outcomes, there becomes a perpetual cycle of 'rebirth' as 'I' am perpetuated from one moment to the next. The 'weak link' in that chain is reactivity/volition. Cessation of the cause releases one from the karmic cycle of 'rebirth' (Rebirth is explained in the link below).
The underlying reason we react, incite volition or generate karma is our understanding of nature is wrong. We are ignorant and deluded and misapprehend the underlying nature of mind and matter. Hence we investigate the body, which is the same in nature as all matter, and the mind, which is is the same in nature as all other minds.
At the bottom is self. The concept not-self or no-self (anatta) - and I have an interesting article about that here which contextualises rebirth.
https://www.buddhanet.net/nutshell09/
(I am not Buddhist BTW - If anything, I'm Anglican)