The Environmental Working Group produces a list of the most pesticide contaminated produce. You may want to consider buying the following 12 items in the organic variety to reduce your exposure.
Grapes (including raisins)
* A small amount of sweet corn, papaya and summer squash sold in the United States is produced from genetically modified seeds. Buy organic varieties of these crops if you want to avoid genetically modified produce.
For the full list https://www.ewg.org/foodnews/full-list.php