Visualisation technique usually used for related to data exploration itself rather that the machine learning technique. Visualisation also used to explain the result, instead of technique. One that was easy to visualise is the result of clustering. Check the link below to see result of t-sne (dimensionality reduction) and its cluster
if x is numerical and y is numerical - Scatter plot
if x is categorical and y is numerical - Box plot
if x is numerical and y is categorical - Density plot
if x is categorical and y is categorical - Mosaic plot
These can be used as a thumb rule for visualization. Additional tip, it is a common practice to do PCA for large datasets.