How to buy online smut manga

As someone who uses Renta as a means to legally obtain manga, having your money slowly deplete as you binge read everything has become a problem. More or less, especially with smut, you have to break the age old saying "don't judge a book by it's cover" and actually start doing it. I have made the mistake of impulse buying and as a poor, jobless, university student, savings are everything. So by making plently of mistakes, I've come up with some rules I follow to ensure I don't buy shitty smut manga.

1. Only purchase in bulk if you know for sure that you are going to read a lot of manga. If you only have a few titles of interest, only purchase what you need. The whole buying points desensitizes you from thinking you're spending money. Giving someone $50 physically doesn't have the same weight as clicking a button and exchanging $50 for 100 points but you still spend the same amount. Don't fall into the extra tickets crap, it isn't really worth it. It's bait.
2. Quickly check the exchange rate of Yen to your currency on google and only bulk buy if needed at optimal times or wait for a better time.
3. For smut, if the girl is naked or really exposed on the cover, don't buy it. Eludes to rape and forced situations. I have encountered some NTR which really irked me and basically dropped that series real fast. I know it's smut and it's supposed to be the whole idea but trust me, they generally suck.
4. If there is more than one guy on the cover, it's probably going to be shit. Love polygons or triangles are rarely done well in shoujo/josei especially if there are numerous guys being pervy assholes.
5. Really long, obscene titles, usually mean the manga is shit.
6. The more cliches in the description the crappier it's going to be.
7. Buy completed manga or one shots only so you know in advance, how much you are going to invest in it.
8. Make sure you preview it before buying. Doesn't help for shorter titles but for longer series, it works well.
9. Harlequins can be decent reads but once you read one story, you've kind of read them all. 

If you follow the bold, you will be able to dodge most of the crappy smut manga. I'm not sure if this can be applied to Yaoi since I don't read it (Boku no Pico scares me) but I'm sure some of the rules could be applied to it. I do break them from time to time since I get tricked by pretty art, hot bishies and the need for manga. Though I generally find that if a manga even breaks one of the bold rules, it does end up turning into shit. 

So let me know if this helped you with purchasing smut manga online. Here is an example of a crappy manga on Renta that is all smut but no plot.

SWEET, SHAMEFUL GUINEA PIG -SADISTIC DOCTOR'S SECRET LABORATORY- - Art nice but has motherfucking rape and ntr. I didn't read the desc. since I gravitated to the doctor theme. Never again. Plus the title is long as fuck so you know this is going to be bad just from how obscene and dehumanising it is. Don't judge me, I WAS TRICKED BY HOT BISHIE DOCTOR IN WHITE LAB COAT AND PRETTY ART OK?  I need to do a better job of not letting my fangurl urges take over.