You can trade jungles and fossils as if they were in the basic card edition as long as you follow the above. Never give out a card for free. Never trade a card you need. You need a strong battle deck to win, you even need those small cards. If you care more about collecting than playing you can disregard this tip.
Energy cards are different.
You can trade a common for an energu if you really need it, but you should always try for more than one. It takes more than one to win. Make many trades and add them to your battle decks. Check for prices before trading. If you are a collector, try for new, better cards and get rid of doubles.