For a 5.5 gallon Sago Palm, what type of soil should be used for container planting on a shady porch and is fertilizer required?

Since you live in USDA Zone 9b, you can grow in the shade. Your container needs to have a light fast draining soil. Lowes sells a Miracle Gro product made specifically for growing palms and other tropicals in containers. This is the mix to use for your Sago. Make sure your container has plenty of drainage as Sago is very prone to root rot. The fertilizer that comes in the mix will last for about 3 to 4 months. After that, light feedings of a balanced 8-8-8 or 10-10-10 slow release fertilizer will work best. You don't want to overfeed the Sago since the roots are easily burned if they get too much nitrogen or heavy organics like manure used on them.

Bed mix to use in a container, azalea, leaf compost or a rose mix. Tropical plants will do well in a sandy soil. this will allow for drainage. Use a 50\50 ratio when planting. Remember HOW BIG the sago will get. You will move this in a couple of years.