If you are in the United States, I would focus on anything American-made, especially at the height of the post-war production and design boom whose style we now call Mid-Century Modern. In addition Danish Modern and other "modern" European styles are very hot.
Another increasingly valuable collectible is vintage jewelry. It is not hard to learn to distinguish good quality from poor quality. As long as your purchase attractive pieces in very good or better condition you really cannot go wrong right now. Pay special attention to any markings on a piece of jewelry. Detecting markings may require a magnifying glass. They are often cleverly placed to present the maker's name without distracting from the design of the piece. Well-known names of collectible quality are Weiss, Trifari, ART, to name a few.
On the west coast, genuine Mexican antique furniture for indoors and outdoors is very hot. Present-day knock offs do not hold much collectible value unless they are exceptionally well made and age well. Pieces made in Mexico in a rustic style and still in good condition are hard to find north of the border, and hence command respectable prices.