I hasn't found a single one even if I looked everywhere. Do I automatically gets cuztomized jutsus when i'm at lvl 10, or what?
You have to do some special missions which reward you with jutsus. *I'll borrow some text from des326 at GameFAQs (these may or may not be in order):
Customizable Jutsu - Dynamic Entry
Location: Talk to Lee at the Memorial Place
Quest: Beat Lees trials
After the talk Lee will vanish. Go to the entrance of Konoha to meet
him another time. When you speak to him he will take you the area you
started RPG Mode. You'll have to do a race around the center passage of
the area and to collect some shiny objects. Finish under 1 minutes to
rank first. Lee will take you back to Konoha. After the talk go back to
the Memorial Place and talk to him again. Now we fight him in VERSUS
Mode. You're NOT allowed to block [R2] and to use items except kunais.
KnJ is allowed and you're slowed down. Win and this quest is over.
Customizable Jutsu - Gais Falcon Kick
Location: Gai in front of the cave
Quest: Race to the end of the cave
After the talk with Gai head into the first room and go to the green
dot. Gai will be waiting there for you. If you accept the missions you
have 5 minutes to reach the middle of the cave. There you'll meet Gai a
second time and he will give you another 5 minutes to reach the end.
When you're there fight him in VERSUS Mode. Gau will have upgrades
[increased speed and attack?]. Win and the quest is done.
Customizable Jutsu - Shikamarus Trap
Location: Temari at the Sand Village Gate
Quest: Get her a item
You can find the item at the second map out of Konoha. There some
platforms to climp up the cliff and on the left one is a glowing
object. Bring the item to her and she will send you to Konoha. Go to
Shikamaru in front of the Hokage Office and answer his questions:
2 2 3 1 3 1 3 1 2 3
Customizable Jutsu - Sakuras Punch
Location: Boy at the Memorial Place
Quest: Beat Sakura in VERSUS Mode
When you talk to him Sakura will join and they both will disappear. Go
to the pond and talk to them. Another race for the glowing spheres will
start. Finish under 30 seconds to win. You start without chakra and
have to finish her with a Jutsu also one bar chakra must be left when
the fight ends.
Customizable Jutsu - Tenten's Weapon Kuchiyose
Important Notice: To trigger this event you need a special item that can be found in a alcove left from the tool shop in the Sand Village
Location: TenTen at Memorial Place
Quest: Get TenTen two items.
After talking to TenTen, go to the Intersection with the save point
 to find a merchant next to the save point. Talk to him. Go to the
cave and in front of the cave you'll see an old man. Talk to him and
then go inside to get a shiny item near the exit on the right side of
the first map (the one with a long bridge). Then go to the Sand Village
and talk to the merchant there. After that, go to the Northwest of big
sand field  and fight some bandits. Return to the merchant and
he'll give you an item. Go back to TenTen and finish the quest.
Customizable Jutsu - Itachi's Gokakyuu no Jutsu
Location: Kakashi at Memorial Place
Quest: Beat Kakashi in VERSUS Mode
After getting the other 5 jutsus talk to him and fight him. You start
without chakra, you can't use jutsus and he has increased speed. Beat
him and he'll give you the jutsu.