Chocks are wedges of sturdy material placed closely against a vehicle's wheels to prevent accidental movement (thanks wiki). They do not raise the tires or level the trailer.

So, to level a trailer from side-to-side you need to raise the wheel on the low side. The cheapest option is some scrap lumber such as 4 x 8 joists cut down to handy sizes – just set it in place and pull the trailer onto the wood. The down side is that it is sometimes not very stable, and its not light weight. Sometimes you can even find scrape lumber or some flat rocks left at the campsite.

A popular option is something like these stack-able plastic blocks. They can be used singularly, or in groups to create a ramp you can drive up onto to gain a few inches. They also make a good base for your tongue or stabilizer jacks when the ground surface is less than ideal, and they are light weight.

Another popular option is the Bal Leveler. It is light weight but does take up a good amount of storage space. You have to manually crank the drive screw with a wrench. Or you can use a power tool, which is yet another thing to carry. It is not a chock but does add to the stability of the trailer somewhat.

The Anderson Levelers are another option. Because of their shape, they do function as a chock to a limited extent and make the trailer less likely to move.

And I agree with Greg that a few additional stabilizer jacks are often a good idea.

When parking, first level from side to side, then chock the wheels, unhook and level front to back using the tongue jack. Use chocks, but note that the camper might roll off of some types of raised platforms if the chocks are not high enough for the raised wheel.  The use of additional stablizing jacks usually prevents this.