I have seen some hunters bury targets in plastic baggies or even in a PVC tube, so the target does not get “lost”. You need to decide that the targets you bury need to stay there. Moving them defeats the purpose, unless you are moving yourself. No need to leave goodies for the next guy.
The following is just my opinion. When using the method of a baggie or pvc tube, the target is not completely touching the soil on all sides. I do not think this will be creating a real world situation. For instance, we all know when iron begins to breakdown and leach into the soil, it will create a halo effect. This halo can sometimes produce a “good signal”. Same rule applies with a coin or a relic. The coin or target will react to the soil around it. With some technology the prolonged contact can make the coin sound better at deeper depths. That is when technology is used to find those targets good or bad. Use this knowledge when making your test garden.
Next, is the most important! Scan the spot for any signal good or bad and REMOVE THEM. This will require you to set your machine to all metal or no discrimination. You need to hear every target! If you can not remove all the signals or there is one that is too large, you may need to choose another spot. Repeat until you have a quiet section for your test garden.
Once you have your spot cleaned. Decide what targets you want to use. I have many coins and numerous relics buried that I have a possibility to find when out detecting. I have one spot with just silver dimes at depths of 4, 8, and 10 inches. I have some dimes touching square nails. Different targets, angles, and depths should be integrated into your “garden”.