How to change barplot in ggplot for R

I have a plot in ggplot that shows me for each category of "rating" the level of price in "bank" and "sistem". This is my code:

##fict
a<-c("rating1","rating2","rating3")
b<-c(1.2,1.2,1.3)
c<-c(1.6,1.4,1.6)

gg<-cbind('rating'=rep(a,2),'price'=c(b,c),'tipo'=rep(c("bank","sistem"),3))
gg<-as.data.frame(gg)


a<-rgb(red=150, green=191, blue=37, maxColorValue = 255)
b<-rgb(red=80, green=113, blue=14, maxColorValue = 255)


    ggplot(gg, aes(x=tipo, y=price,width=1)) +   
      geom_bar(position='stack', stat='identity', fill=c(b,a), color='black') +
      facet_wrap( ~ rating)+
      theme_bw() +  theme(axis.line = element_line(colour = "black"),
         panel.grid.major = element_blank(),
       panel.grid.minor = element_blank(),
       panel.border = element_blank(),
       panel.background = element_blank(),
    strip.background = element_rect(colour = 'white', fill = 'white', size = 3),
    axis.title.y=element_text(vjust=0.19),
    axis.title.x=element_text(vjust=0.19)
    #strip.text.x = element_text(colour = 'red', angle = 45, size = 10, hjust = 0.5, vjust = 0.5, face = 'bold')
    ) + xlab("My x label") +
      ylab("My y label") +
    labs(title = 'difference')

This code generates my plot.

I'd like to change 3 things:

• I'd like that the labels rating shows in the bottom
• I'd like that the "bank" and "sistem" labels disappear and change it with the legend with colors for bank and sistem.
• If it's possible also put the legend under the x-axis title in horizontal way

Thank you