[G-Dog]

an error I noticed with part II code is your usage of price, and plugin_on. The way you defined them they are pcvars thus instead of

if (plugin_on == 1)

you should have

if (get_pcvar_num(plugin_on) == 1)

same for price. To use them instead the way that you did you would have to do this in plugin_init

    register_cvar("amx_tutorial_plugin", "1")
    register_cvar("amx_tutorial_price", "4000")
    plugin_on = get_cvar_num("amx_tutorial_plugin")
    price = get_cvar_num("amx_tutorial_price")

edit:
yes do

cs_set_user_money(id, money - get_pcvar_num(price))

and upon better inspection of the code since the mass comments overwhelmed everything, I would suggest that you first check if the user has enough money to afford the steroids before setting the health and gravity. Also rather than just arbitrarily setting heath to 150 I would instead add 50 health since someone could use the command just before dieing to reset health to max each time.

public steroids(id)
{
    if ( !get_pcvar_num(plugin_on) ) {	
    /*
    ! operator means false which equates to 0 in numerical sense so this equates
    to if ( get_pcvar_num(plugin_on) == 0 )
    */	
        client_print(id, print_chat, "Steroids currently disabled");
        return;		//ends the function on the spot
    }
    new money = cs_get_user_money(id);
    new cost = get_pcvar_num(price);	//rather than calling get_pcvar_num 3 times, store it to a variable
    if ( money >= cost )	//run a check on if user has enough cach
    {  
        cs_set_user_money(id, money - cost);  
        set_user_health(id, ( get_user_health(id)+50 ) );	//sets user health 50 points greater tehn current health incase they have more or less than starting 100
        set_user_gravity(id, 0.50 );
        client_print(id, print_chat, "You just purchased some steroids, dude!");
    }
    else 	//if they didn't have enough cash display a message stating how much more they need
    	client_print(id, print_chat, "Sorry you need %d more cash to afford steroids", cost-money);
}