Kamerra is right. Depending on the tradition will depend on the type of initiation, how long you wait, and so on and so forth.
The usual study for a tradition wiccan at a dedicate level (or first degree depending on tradition) is 1 year and 1 day.
Depending on the tradition for the 2nd degree, it too is usually 1 year and 1 day, I've heard of some that takes 1 year and 2 days. and other that are 2 years.
Basically, when if you do a self initiation, it's between you and the Goddess and God, or w/e you follow. It's your personal way of telling deity that you have dedicated your life to trying to live as closely to divinity as possible. A good life. It's also a time to ask for blessings.
Here's an example of a self initiation from - http://paganwiccan.about.com/od/wiccanandpaganrituals/ht/Self_Dedication.htm
By the very definition of the word, you can?t initiate yourself, because to initiate requires more than one person. But what you CAN do is dedicate yourself to your path and to the gods you have chosen to follow. For many people, doing this as part of a formal ritual helps to cement their relationship with the Divine. Some people choose to wait until they have studied for a year and a day before having a formal self-dedication rite. It?s entirely up to you.
You may want to wait until the time of the new moon to perform this self-dedication, because it is a time of new beginnings. Bear in mind that self-dedication is a commitment you are making; it should not be done at random or without significant thought beforehand.
This goal of this rite is to bring the dedicant closer to the Divine, as well as to declare your connection to your spiritual path.
You should perform this ritual skyclad, if at all possible. Find a place that is quiet, private, and free of distractions. Turn off your cell phone and send the kids out to play if you have to. You will need the following items:
Half a teaspoon of salt
A white candle
Begin by grounding yourself. Find your inner peace, and become good and relaxed. Shut out all the things from your mundane life that distract you -- forget for a while about paying the bills, your son?s baseball practice, and whether or not you fed the cat. Focus only on yourself, and the tranquility you?re entitled to.
When you?re ready to proceed, sprinkle the salt on the floor or ground, and stand on it.
Light your white candle, and feel the warmth of the flame. Look into the glow of the fire and think about what goals you have for yourself on your spiritual journey. Think about your motivations for performing this self-dedication.
Stand before your altar, and say:
I am a child of the gods, and I ask them to bless me.
Dip your finger into the blessing oil, and with eyes closed, anoint your forehead. Some people do this by tracing a pentagram on the skin with the oil. Say:
May my mind be blessed, so that I can accept the wisdom of the gods.
Anoint the eyelids (be careful here!) and say:
May my eyes be blessed, so I can see my way clearly upon this path.
Anoint the tip of your nose with the oil, and say:
May my nose be blessed, so I can breathe in the essence of all that is Divine.
Anoint your lips, and say:
May my lips be blessed, so I may always speak with honor and respect.
Anoint your chest, and say:
May my heart be blessed, so I may love and be loved.
Anoint the tops of your hands, and say:
May my hands be blessed, so that I may use them to heal and help others.
Anoint your genital area, and say:
May my womb be blessed, so that I may honor the creation of life.
Anoint the soles of your feet, and say:
May my feet be blessed, so that I may walk side by side with the Divine.
If you have specific deities you follow, pledge your loyalty to them now. Otherwise, you can use simply ?God and Goddess?, or ?Mother and Father?. Say:
Tonight, I pledge my dedication to the God and Goddess. I will walk with them beside me, and ask them to guide me on this journey. I pledge to honor them, and ask that they allow me to grow closer to them. As I will, so it shall be.
Take some time to meditate. Feel the afterglow of the ritual, and feel the energy of the gods around you. You have brought yourself to the attention of the Divine, so they will be keeping an eye on you. Accept the gift of their wisdom.
Here's A recipe for Blessing Oil-
To make Blessing Oil, use 1/8 Cup base oil of your choice. Add the following:
5 drops Sandalwood
2 drops Camphor
1 drop Orange
1 drop Patchouli
As you blend the oils, visualize your intent, and take in the aroma. Know that this oil is sacred and magical. Label, date, and store in a cool, dark place.