=================
Depends how far you want to go. (not sure if I intend that pun or not)

Since this is something that is planned, I usually do all related items
to keep the car in top condition.
spark plugs, valve cover gasket, ck. valve clearances, replace spark
plug tube seals, replace distributor O ring, ck. spark plug wires and
replace with cap and rotor if needed, thermostat, PCV valve and grommet
(while the valve cover is off to avoid broken pieces falling inside),
gas cap, coolant, transmission and differential fluid, brake fluid, ck.
battery level and state of charge, replace accessory drive belts, for
peace of mind I would also replace the idler and tensioner bearings,
but you could check first for smooth quiet turning by hand, replace
engine oil seals: crankshaft oil seal, oil pump oil seal and O ring,
camshaft oil seal, (that one is sort of optional because the cam turns
at half speed and is easiest replaced with a special tool to press in
near limited clearance from the strut tower), ck. chassis mounting bolt
torque, ck. alternator brushes, replace if needed, change power
steering fluid, ck brakes, ck ball joints, ck steering free play.
BTW, I use all Toyota parts. I shopped the parts list on the Internet
and found an out of state dealer with excellent service and reasonable
prices, then subsequently simply leveled with the local parts manager
and he will usually match their prices especially when I'm ordering
more than a few parts.
With Toyota parts you're getting an exact replacement. For the few
dollars extra, I often replace the fasteners, too. Wish I'd changed the
water pump bolts last time, but will get them next time. There was a
small amount of corrosion on some of them, and it is a lot easier to
replace them early than deal with removing them if they break - like on
my '77 Toyota truck - took lots of soaking in Kroil, and lots of
patience.

I listed the following the a 5SFE earlier. Typically a timing belt job
should include them. Of course, there are other maintenance items
performed accordingly.

(www.rockauto.com prices for 5SFE, similar to the 3SFE)
GATES TCK199 (kit of timing belt with two pulleys and instruction)
$84.79
GATES Part # K030295 PS belt $4.32
GATES Part # K050435 Alt/AC $12.12
FEL-PRO TCS45641 Cam seal $4.11
FEL-PRO TCS45920 Crank seal $6.04
BCA Part # 221820 Oil pump seal $2.71
FEL-PRO VS50304R valve cover gasket set $13.94
BECK/ARNLEY 0396428 $1.87
AISIN (Toyota #16110-79185) water pump $58.79

rockauto.com doesn't list the Airtex water pump, but they carry the
Aisin which also makes the OEM pump. The local NAPA store carries the
Airtex with lifetime warranty and that's where I get my water pumps.

Follow the instructions to the letter when changing the timing belt.
There is a brief instruction sheet included with each Gates timing kit.