How can I get to the chapter 23 and find everything I need...?

Chapter 23 is the Empire of Ice adventure pack. It is fairly tough. Best method for manuevering a skylander on ICE is go slow. Take short steps ONE at a time otherwise you slide into the ice holes and have to start over.

There isn't really anything you NEED in order to complete the level, except gathering up all the pieces of the catapult. The other stuff like treasure, hats, and gems are stuff to add to your collection. The SOUL GEM is needed if you are going to upgrade Slam Bam all the way to the top. That LAST purchase requires the Soul Gem from Empire of Ice.

The BEST solution I have found for MANUEVERING within the Empire of Ice is to use your "Water Skylander" ONLY to get INTO the empire of Ice, but once inside, SWITCH to a Skylander that can FLY and HOVER. They still fall in the holes (when you fly over a hole), but you DO have a little better control and can stop "in air" a little easier. You will still need to FLY slowly, but is is much easier with a flying skylander, than with a walking guy. It took me several tries to make it through EMPIRE OF ICE using Slam Bam. I tried other skylanders later to see if any others would have better luck. None did, until the idea hit me to try FLYING. That was the trick needed. When my wife tried, I suggested she use a FLYING Skylander as soon as she could switch. The was able to get everything except the ICE BOWL in one pass. That Ice Bowl is tough and is mostly a matter of LUCK not skill anyway. If you don't make it, just go right back through the gate and try again. 15,20,or 30 tries and you will eventually get lucky and solve it. When you RETURN, after successfully completing the Ice Bowl, your reward will be at the "teleport back" location. Most of the other stuff is fairly easy to find, because you can see it. The problem is you have such a hard time getting TO the stuff because of the ice. Which is why the FLYING Skylander is probably your best option.

There is one gate that needs a bomb to open. Clear the area first, then make your run, either with a walking skylander or better with a flying one. The distance is right on the limit of what a walking guy can do before the bomb explodes. You will have to throw the bomb at the very last second. If you use a flying skylander, they cover the distance faster so you have a little more time cushion. When using skylanders to deliver bombs. The exploding bomb will not hurt the skylander, but the problem is that you probably take too long (slightly) getting the bomb to the target. PRACTICE the run a couple of times until you KNOW it by heart and can make all the turns without running into any walls or other obstacles. Then grab the bomb and make your run.