Buddhism has the idea of the three jewels: Buddha, Dharma, Sangha.
You said "I believe in Buddha and his philosophy" so that's two of them, i.e. Buddha, and Dharma.
There are parts e.g. in the Dhammapada which suggest it's better to be alone than with a fool:
If for company you cannot find a wise and prudent friend who leads a good life, then, like a king who leaves behind a conquered kingdom, or like a lone elephant in the elephant forest, you should go your way alone.
But Buddhism might also support (or encourage or recommend) friendship. For example, the Upaddha Sutta says,
I have heard that on one occasion the Blessed One was living among the Sakyans. Now there is a Sakyan town named Sakkara. There Ven. Ananda went to the Blessed One and, on arrival, having bowed down to the Blessed One, sat to one side. As he was sitting there, Ven. Ananda said to the Blessed One, "This is half of the holy life, lord: admirable friendship, admirable companionship, admirable camaraderie."
"Don't say that, Ananda. Don't say that. Admirable friendship, admirable companionship, admirable camaraderie is actually the whole of the holy life. When a monk has admirable people as friends, companions, & comrades, he can be expected to develop & pursue the noble eightfold path.
"And how does etc.
Note: As AN 8.54 points out, this means not only associating with good people, but also learning from them and emulating their good qualities.