It's all about budget. How much are you willing to spend? Also don't rely on spoonfed information. Do your own research and find things out yourself and only ask if you need clarification. Otherwise sooner or later people are going to take advantage of you or take you for a joyride - especially shops and mechanics.
If you want to change engine since it's a 1.3 the biggest you can go is 1.6. So you can't really consider the 4G93 1.8, the largest you can go legally is 4G92. DOHC 4G92 is the largest you can go. Just the upgrade in engine alone is going to cost around 2k give or take and the workmanship to install about 500 to 1k depending on the condition of the engine. Seals, gaskets, bolts, nuts, everything will need to be inspected due to the age of the engine.
Also since you're a newbie, don't always pursue power. I know some seriously fast Myvi drivers and automatic Satria drivers. Upgrading your driving skills will do much more than constantly always pursuing power. If you have a favorite corner you like to layan take note of your speed and how you drive in that corner and keep trying to go faster or manage the corner better without scaring the crap out of yourself. Then once you think you've reached the limit of your skills, start upgrading suspension, tyres, brakes, intake and all these sorta small things. A good set of brake pads will significantly help shift weight around, a good set of tyres will help you corner harder and faster, etc etc.
Personally I believe you should try to maximise and push the limits of your car before you go nuts about power and all. Start with suspension, tyres, brakes and only lastly go engine once you've mastered the 1.3. Giving you a 1.6 now would be like giving a toddler a gun. Would the toddler know it's a gun? Sure but would he know how to use it properly without the kickback smacking the gun in his face? Probably not.