Unless you are bringing in something illegal, declare it all.

As long as it doesn't look like you're bringing enough stuff to begin/stock a business, or that the value of your goods isn't astronomical, they will almost certainly wave you through.

If you fail to declare goods and are caught, not only will you likely be fined, but you'll also likely be flagged for a trip to the Red line for the forseeable future.

Leave the smuggling to the professionals.