I'm going to the store now to buying Soil for my newly fig tree,
what type of soil mix do I need for a 5gal or 15 gal pot ?

2nd question : how often do I water my rooted cuttings in my 16oz cups

thank you in advance

This was very helpful for me:  http://figs4funforum.websitetoolbox.com/post/Which-soil-would-you-use-for-pots-Pics-to-choose-from...-6251400

you just have to try few. al's 5:1:1 makes sense. but that takes getting things and mixing them togather. i heard some of the premium soil mixes work very well. some others have used MG soil with acceptable results. balance between what is available, cost, and how far you are willing to go for your figs. i just get stuff that's in our local HD and lowe's. just found organic gardening shop here so i get better price on the perlite and peat moss.

also I would like to ask how muchvermiculate and perlite do I need for new rooted cutting when I plant them in my 16 oz cups?

you don't need drainage rock. but some people still use them. more to prevent soils from going out of the drainage hole i think.

from 16 oz cup, you want about 1:1 perlite and seedling soil. some people go higher with perlite. but i'm finding that in 16 oz cup, 50/50 give good drainage and water retention. make sure there are hole in the cup to drain water and possibly circulate the air. quickest way to kill a cutting is get the soil to hold water too long and drown the roots.

Search for posts by Al Tapla here and in Garden web's Container Gardening forums.  They give you a great understanding of how to think about soils and some suggestions of mixes.  His gritty mix will need to be watered more than once per day in mid summer so I don't recommend that one.  And anywhere he says "sand" I use perlite, mainly for weight.  :)

As has been pointed out, there are tons of mixes to try. If you want an easy no brainer mix buy Promix HP (High Porosity) It's fine for newly rooted starts and fine for grown plants in large pots. No need to add anything. 

I agree with Pete that you do not need drainage rock. They serve no purpose in reality. If you have a 12 inch tall container and put in 2 inches of rock, you now have a 10 inch tall container in terms of how you growth media behaves. The drainage holes in your container supply the avenue for water drainage. Rocks are unnecessary.

If you really want to understand potting soils and the choices that are out there, I would encourage spending some time on the North Carolina State University Crop Science website.
http://www.nurserycropscience.info/
In my opinion, these people are the best in the world at understanding and developing potting soils for growing in containers. A couple of links that I find really helpful are:
http://www.nurserycropscience.info/substrates/pine-bark/other-references/container-soils-and-soiless-media-bilderback-1982.pdf/view
http://www.nurserycropscience.info/substrates/physical-properties/technical-pubs/bilderback-et-al-2005-healthy-substrates-need.pdf/view

I would advise against listening to the advice of Tapla. He has a couple of formulas out there for 2 media (5-1-1 and gritty) that will work with the right amount of attention. You can follow his empirically derived instructions and be successful. Most of his scientific explanations are simply wrong and unfortunately very misleading if you wish to understand how potting soils function to be a very successful grower. I apologize for bringing up negative stuff. But, my observation is people who encounter problems based on factors that are poorly understood by Tapla are not treated very nicely and usually receive no help. Others may disagree with that opinion.

I just picked up some Pro-Mix HP from lowes today. I wanted a fairly brainless (for me) medium for my potted trees. I don't have room to have lots of different bags of mediums to play with. I've heard good things about this one so I hope the little fig trees like it!

for cuttings in cups that have been placed into humidity bin.. after initial watering or wet soil.. i don't water for about 2-3 months. but i check almost everyday to see if they need water. once the roots are there and the top is growing, it will start to use water more quickly and you will need to start watering very little after few days. however, during the initial phase, i haven't really had any reason to water. the roots were not picking up the water too much and leaves weren't there to perspire the water away. becareful with watering during the initial stage. it's tempting, but too much water will rot the root and the cutting.

best way to know how often you have to water is monitoring the cup everyday or two.

I agree 100% with Pete.  Just because you see roots does not mean they are "productive" and are feeding the system.  Same for the leaves.  Easiest way to kill a cutting at this point is to water.  After killing about 80% of a batch I did 6 weeks ago, I have taken to only putting about 1 tbs of water every two weeks in the cups and I am keeping them either "domed" or in a bin.  About every couple of days, I air out the bin for 30-40 minutes.  On the domes, I have a couple of holes near the bottom and 1 hole on the very top (remember, the cup is upside down for a dome) so that fresh air can get in.  So far, I have not "drowned" any cuttings with too much love (water...).

Watering will greatly depend on how humid the environment is.  As mentioned, check them every day or two and evaluate their habits.  There are no rules on how often to water, but the point is to keep the soil barely damp.  I check for condensation on the inside of the clear cups, as well as how heavy the cup feels.  Honestly, the more you study them, the more you'll learn what it needs.  It's definitely a learning process.

And for another curve ball...
A good example on how each cutting is different...I had assumed one of my cuttings was damp enough, and the next day, all the leaves had drooped down.  I immediately fed it some water, and within 24 hours, it was alive and well.  So again, watch them very closely!