Advice: Trying Ketamine for the first time for treatment-resistant depression.

Like the title says I am planning on taking Ketamine for the first time to treat my ongoing battle with depression/anxiety. However, because the price of infusions is so high (the cheapest in my area is $400), I've decided to do it on my own. From what I've heard Ketamine is relatively safe, but I am trying to be as diligent as possible in learning as much as I can about it (I'm currently on mirtazapine and sertraline and from what I've read those drugs will not cause a contraindication). Anyways so my friend is going down to mexico to get some medication and I asked him if he could get me some ketamine from the pharmacy. If he is able to purchase it, what form of ketamine would he be able to get (liquid, lozenges, spray)? Do they sell non-liquid ketamine? If so, which type would you recommend? Also depending on the type which dosage should I take? Any advice is appreciated!