If you have faith to just practice Guru Rinpoche, that's enough
The essence of Guru Rinpoche is the same as the essence of Buddha Shakyamuni. In Sutrayana there’s Buddha Shakyamuni. In Tantrayana there’s [Buddha] Padmasambhava. But in fact they’re the same. Guru Rinpoche, Padmasambhava, is from the Lotus Family. I’d like to say Amitabha, Green Tara, Avaloskitesvara are also from the same family, Lotus Family. So we can say that Guru Rinpoche is the embodiment of the Buddhas in the 10 directions and three times. Therefore, actually it is enough for one person to just practice Guru Rinpoche.
But since we have different karmic connections with different deities, and we have different faiths in different deities, and we have different desires for different things, so we need many different deities. We need all of these: Guru, Yidam, Dakini, and Protectors. But sometimes having too many practices can cause problems, because we can’t focus on [one] thing. When we try to do too many things, try to accomplish too many things, then we lose power, and we’ll probably achieve results smaller. In the tradition of India, one person one Deity, one person one path. In Tibet, one person many Deities, one person many paths. Therefore, the Indian masters are making fun of Tibetan practitioners: because they have too many Deities, so they cannot have confidence in one Deity. Sometimes that causes problems. So if you have faith to just practice Guru Rinpoche, that’s enough.
Hungkar Dorje Rinpoche, “Devotion To Guru Rinpoche – Key To Siddhis”