TextLabel not showing strings from a table?

It's exactly what the error message says. The Text property expected a string value, but you gave it a table value. If you want to make a text read strings from a table, you're going to have to iterate the table with a for loop, and assign each one of those individual texts to that textlabel. Like this:

local Texts = {
    "TESTING",
    "MEMES"
}

for i,v in ipairs(Texts)do
    MainBarText.Text = v
    wait(1) -- probably going to need this so we can actually see the texts changing
end

for i = 0,1,0.1 do -- Turn invisible
    MainBarText.TextTransparency = i
    wait()
end

-- again

for i,v in ipairs(Texts)do
    MainBarText.Text = v
    wait(1) 
end

for i = 1,0,-0.1 do
    MainBarText.TextTransparency = i
    wait()
end

Now, we could actually make this a bit cleaner by making a function that changes the text for us, using the same for loop. Like this:

local Texts = {
    "TESTING",
    "MEMES"
}

local function IterateTexts(Table, Time)
    for i,v in ipairs(Table)do
        MainBarText.Text = v
        wait(Time)
    end
end

IterateTexts(Texts, 1) -- Going through the "Texts" table, changing the text every 1 second.

for i = 0,1,0.1 do -- Turn invisible
    MainBarText.TextTransparency = i
    wait()
end

IterateTexts(Texts, 1)

for i = 1,0,-0.1 do
    MainBarText.TextTransparency = i
    wait()
end

Hope this helped.