Let me see. Your touch screen needs 2 chip selects. So it uses up Rpi's only two chip selects CS0, CS1.
There are a couple of ways to get around. See the post below for more details.
SPI AND CHIP SELECT PINS - planeta9999 2013-Jan-23
I actually tried all the things suggested in the above post, and they all work. I have also tried other things as briefly described below.
"Create" more SPI channels by fiddling the 3V3 to 5V0 logical level converter such as TSX0104. I use 4 TSX0104 converters, each enabled by a Rpi GPIO pin. So by enabling one of the 4 TSX0104s, I can select one of the four SPI channels. Of course you can create more SPI channels by using more TSX004s. This is not soft ware bit banging, because the real Rpi SPI channel hardware is used. In other words, almost as fast as the original real Rpi SPI.
Same as 1. above, but instead of using Rpi GPIO pins, use I2C MCP23017 IO port expander. MCP23017 has 16 GPIO pins. So you can select any one of 16 deMUX SPI channels.
Of course you can use more MCP23017. I once tried 8 MCP23017s to select 16 x 8 = 128 devices, but it get unstable when you scale up more than 2 MCP23017s.
But there is one catch. In the above methods, you forget the Rpi chip selects (just disconnect them), and use you own chip selects. This works for all the SPI devices I work so far, except those like WaveShare touch LCD, which uses their own drivers, insisting to use Rpi's CS0, CS1.
Of course you can mess around WaveShare's driver software, but that is very difficult for newbies, and not linux version invariant.
Now for newbies, I usually recommend the following.
Forget the very old, low 10/12 bit resolution SPI MCP3x0y,
Use the new 16/24 bit I2C ADCs instead.
In the brave I2C new world, you have too many more devices to choose, and that is why the SPI guys are getting so jealous. And that is why I2C is getting so popular over SPI (so many more I2C modules, comparing with SPI).
So check out AdaFruit and SparkFun what new I2C ADCs they are recommending.
WaveShare 3.5inch RPi LCD (A), 480x320 US$23.99
WaveShare 3.5inch RPi LCD Technical Notes
320 x 480, 8:5, 65536 colours, TFT, Backlight LED,
SPI, Touch Screen Resistive, Controller XPT2046,
PIN NO. SYMBOL DESCRIPTION
11 TP_IRQ Touch Panel interrupt, touch detect low
18 LCD_RS Instruction/Data Register selection
22 RST Reset
19 LCD_SI / TP_SI SPI data input of LCD/Touch Panel
21 TP_SO SPI data output of Touch Panel
23 LCD_SCK / TP_SCK SPI clock of LCD/Touch Panel
24 LCD_CS LCD chip selection, low active
26 TP_CS Touch Panel chip selection, low active
If you don't wish to replace SPI MCP3008 by another I2C ADC, you can consider use Rpi's second set of SPI. Again this is hard for newbies. Below is a picture for you to start exploring.