Since most house plants are kept in relatively small pots, the most convenient trowel you can get is one that is less than 3″ at the top of the blade. They are inexpensive and easily available.
Bulb sprayers come in varying sizes and are used to wet the foliage of most plants. For house plants you should buy the smallest kind. A substitute for the sprayer, usable though not quite so efficient, is the atomizer such as the ones sold to spray perfume or medicine
Every home gardener should have a ball of light twine at hand for use in tying up climbing plants and in tying back the unruly plant.