This is, I believe, a difficult topic for most people. Some believe initiation is an absolute must and are desperate to find an Occult group to get initiated into, while some others dismiss it completely.
First of all, I will mention that I believe both truths are correct. However, I will mostly talk about my own personal experiences, with the hope someone willfind it at least a little bit useful or at the very least, interesting.
Initiation means a new beginning, and it has several effects: first, putting the candidate into the group mind or egregore or the order/coven/etc so the new initiate can tap into that reservoir of energy, second, as a welcome into the group and third (most importantly I believe), making profound changes into the initiate's life.
Now, there are groups offering two types of initiation: physical, within a temple with officers and the whole ceremonial and the so-called astral initiation.
The most controversial one is the astral initiation. I will share with you my own personal opinion.
Astral initiations do not work magically.
While there are forces you can get in touch astrally and receive initiations from in the astral plane, that only happens with extremely advanced practitioners, not beginners.
Groups that offer true astral initiations online are a scam to steal money from well intentioned people.
Let's talk about the biggest magical western tradition since the XIX century, which puts a lot of emphasis on initiation, the Hermetic Order of the Golden Dawn.
The Golden Dawn (GD for short)has a series of initiations, the 0=0 Neophyte, 1=10 Zelator, 2=9 Theoricus, 3=8 Practicus and 4=7 Philosophus. Leaving the 0=0 aside, the for grades are related to the four classical elements of Earth, Aire, Water and Fire respectively. Then comes the Portal Grade, which acts as a intermediate grade between the GD and the Rosae Ruboe et Aurea Crucis or Second Order, which are the grades 5=6 Adeptus Minor, 6=5 Adeptus Major and 7=4 Adeptus Exemptus.
All these grades correspond to the Sephiroth of the Tree of Life.
Now, from my experience with initiation into the GD I will tell you this: initiation into the GD is not a pleasant thing. The first (0=0) initiation you will not feel surrounded by love or white light or whatever the hell you think intiation will give you. I felt scared sh**less, I wanted to puke, couldn't speak and it left my bedridden for a couple days. While I can't by my own oath talk about specifics, I can tell you initiation into the 0=0 grade is a day you will not forget, and while it put me through hell, looking back, I think of it as a beautiful day.
And it's not my life began to transform for the better. Yes, indeed some things did get better, while others took a turn for the worse...actually, it turned into a living hell. I guess that's the Judgement of Osiris the Per-Em-Hru (Egyptian Book of the Dead) talks about...
However, since I practised the GD rituals (such as the Lesser Banishing Ritual of the Pentagram) before my initiation, I can honestly say being initiated does change a lot. Being into the GD egregore gives the ritual a whole different meaning and power I wasn't able to realise before.
The week following my initiation I said to myself "hey, let's do the LBRP, see if something actually happened"..and it did. So I can honestly say, initiation in an actual temple, with officers and the whole thing does work and it does empower you.
Now, initiation does increase your capacity for magic, I believe because it makes specific changes into the sphere of sensation that unlocks several energies or unconscious complexes (is there really a difference?) while also let's you tap into the group's energy reservoir.
So, to be concise, if an initiation didn't change you even a bit, it didn't work. Initiation means a new beginning, a new life, not keeping the same old life you used to have. In order to become this new person, the old you needs to die.
Now, do I believe initiation is mandatory for practising magic? No. Is it a helpful boost? Unbelieveable so. Is it painful? Yup, it kills you and puts you back together again. Is it for everyone? No, no way, but that's for you to decide.