Who is a real Guru?
Planet Jupiter is the DevaGuru and Venus is the AsuraGuru. Forget about the differences between them and just focus on that one place where they meet with mutual understanding. Yes, Pisces is that place, ruled by Jupiter where Venus gets exalted. What’s the meaning of Pisces? There is no meaning and that's the meaning of it. It's the abstract world with no set principles and boundaries. It's the ocean where you can find anything and everything. It's the universe, union in versatility, the home of good, bad and ugly but everything thrives at one place regardless of their innate differences. That's the nature of a real Guru.
It's hard to find a real guru/yogi in modern times and most of the time the people who call themselves as gurus/yogis aren't the real ones.
The real Guru teaches you to find wisdom, shows you the path to let go of your differences so that you’ll become free (moksha), but in order to let go of differences you need to understand the differences first. That's why Sagittarius (natural 9th house), the sign of dharma is the first sign in the zodiac belt ruled by Jupiter. Dharma is based on the principles of nature. Dharma in sanskrit means law, justice, religion, morality, purpose and duty. Dharma teaches us rules and regulations of life bestowed by nature. But the same dharma evolves in a rather self contradicting way based on time, place and situations. That's why Pisces (natural 12th) is the second sign ruled by Jupiter. For ex., religion says wake up at brahma muhurta and recite mantras in reverence of Sun God (Surya) then follow your material duties but spirituality is about no difference between God and material, all are one and same and a spiritual Guru sees God in anything and everything. This is the difference between two Gurus. First one teaches you the basic knowledge and its differences and the second teaches you to grow and evolve with it. Learning the difference is Sagittarius and evolving through the difference is Pisces. If Sagittarius says dharma is set rules and principles then Pisces says dharma doesn't have boundaries. Yet both are ruled by Jupiter.
Religion says wake up at brahma muhurta and recite mantras in reverence of Sun God (Surya) then follow your daily material duties but spirituality is about no difference between God and material, all are one and same and a spiritual Guru sees God in anything and everything.
This can be interpreted easily through an excerpt from Ramayana. The conversation between Sage Vishwamitra and Lord Ram while walking through the forest:
Sage Vishwamitra: Look, tadaka is charging towards us, kill her
Lord Ram: What? I won't, because Guru Vashishta taught us that killing a woman isn’t a dharmic act.
Sage Vishwamitra: She killed everyone in my village.
Lord Ram: But she left you?
Sage: I'm skinny due to austere penance so she left me but killed everyone.
Lord Ram: Still it seems wrong.
Sage: Dharma isn't just what you learned my dear son, it grows and evolves with time, place and situations. Tadaka is a woman just by appearance but in reality she's a rakshas (a monster), she ate and tore apart everyone in her path. So killing her is the only dharmic act.
Lord Ram: Apologies master, from now on I’ll not disobey your words.
Puranas and Itihasas teach us that there are two types of Gurus. First Guru is the one who teaches you dharma (Sagittarius), your first light of life, that's why astrology also stems from the 9th house and second is who takes you towards the path of spirituality and moksha (Pisces, the heart of Sagittarius). Both are important and are different sides of the same coin. Shastras show (not necessarily say) that one needs two different Gurus in life because if learning dharma is high school then learning its evolutions is doctorate.
Note: It's not necessary that your first Guru should be a spiritual one but he/she certainly has to be a dharmic one. That's what Jupiter teaches us here.