It takes more effort to get 18 orders than to get 90 families. Then, get a feel for how different families within the larger order look, so that you are less likely to obtain redundant specimens of the same family. You can find many by holding a net under vegetation and shaking or thrashing the vegetation so that insects fall into the net. Many come to flowers to feed. You can obtain many kinds of beetles and other forms by scooping leaf litter onto a sheet, and picking through it, while watching for others that crawl away over the sheet.
Many insects live inside things, such as rolled leaves, flowers, rotten wild, mushrooms, etc.
Look for certain interesting species in or under dead animals or rotting vegetation. Many more insects surround you than are easily seen. Do no focus just on capturing individual insects that you see. The various techniques mentioned above will reveal many more. If you collect in parks or other locations where restrictions might apply, be sure to ask permission of guards or officials.