First of all, you should understand where the IVs are coming from and the assumptions made in the model to derive the values.
IVs are solved through option pricing models by the given market prices of the options. Many of the option pricing models assume underlying securities are lognormally distributed, for example BS model. However, the market participants disagree on that. Volatility smiles(smirks) actually represent how market participants disagree on the model, because if the market prices of options are exactly same as BS model, the IVs smiles are actually a flat line.
So buying an option from a strike with lower IV doesn't mean you get a "better deal", because the distribution of underlying might be totally different from the model used to solve IV. Also, options prices(also IVs) are determined by many factors such as type of securities(FX are more like smile but equities indexes are more like smirk), supply-demand, market scenarios and idiosyncratic events. So staticly look at the IV skew doesn't tell you if it's truely, and relatively, cheap or expensive.
However, looking at the dynamics of skew change might tell you the option is relatively cheap or expensive comparing other strikes. Lots of hedge funds' option groups are actually trading for skews. There are a few skew trading strategies you can easily find online