No language is easy to learn, but at the same time no language is difficult if you are passionate enough and have the right kind of resources and tools. A dictionary serves the best purpose if it is comprehensive and have various kinds of elements that are required to understand the nature and application of the words.
While learning Sanskrit through English language, a lot of students from India and foreign counties find it difficult to decide on a good dictionaries. Though there are several tries made for an online dictionaries but none of them is good and reliable. I have tried many of them but none serves the purpose.
For that matter, I have compiled a list of Sanskrit-English dictionaries that you can buy online.
By far, this is best dictionary that I have come across. It is comprehensive and offers various insights about the words and their usage. Related terms are also offered for a particular word. Published by Motilal Banarasi Das and available in hardcover.
A very competent dictionary often referred as the best in the market. Touted as equal to M. Monier-Williams dictionary but bit cheaper in price, it offers various suggestions and grammatical usage of words.
A very good dictionary oriented to provide deeper knowledge to Sanskrit students about various epics including the Ramayana and Mahabharata, Puranas and Upapuranas, Smrti and Niti literature, Darsanas or Systems of Philosophy. The dictionary includes a plethora of words that occurred post-Vedic literature.
If you want to taste Hindi and English together while learning Sanskrit, this dictionary will be good option as it has over 6,000 entries. You can learn all Sanskrit roots, etymologies, inflections, genders, numbers and cases, which are provided along with examples from classical as well as modern literature of Sanskrit language.