Unang-una...i-click mo yung CAPS LOCK botton ng key board mo...rude ang all caps on a typical forum like this.
Then, consider mo muna ang actual desire mo why you want to do a Stage 1 upgrade....if you plan to race...forget it....kasi your tranny na A/T won't do you no good (unless steptronic yan).
Then kung ang gusto mo lang naman ay maging isang ganap na riceboy...well it would probably cost you about P10K on the minimum....cone type K&N filters and the mandrell bent pipes that goes well with this (I don't know kung merun pang sentra series 2) would be about P5-7K na dati.
Then upgrading your pipes would mean total fabrication ng headers up to the exhaust. Depende sa brand of exhaust muffler na gagamitin mo and if ang pipe na gusto mo ay ordinary o stainless type...ang price mo can be about P2K (pinakamura kasi generic pipes and muffler at malamang ay hindi mandrel bent) to as high as more than P10K.
Cons...PERA lang siguro, isang malaking gastos.
Pros...a big GRIN on your face when ever you see people stare at you when you pass by them (just don't ask me if they are laughing at you or nabilib sa oto mo, coz I don't know it either). Your car would sound fast (but will really never be that fast enough).
IMO Sentra Series II is a good sleeper car kung naka 1.6L engine ito at manual tranny...pero to convert it to really good fast car (not necessarily racing)...you'd be in for a big gastos lang. I saw one kapitbahay of mine...he added a turbo with intercooler sa series 2 nya...well it was fast and nice and rice looking...but talo pa rin sya ng nakahonda (with similar gastos in mods)...so eventually he sold it and bought a honda.
Why not keep it stock, at most upgrade the airfilter (K&N will have the stock filter malamang...don't go for the cone type).
The best I go would be buy her a new set of shoes (mags and tires) ...lowering it is an option kasi hindi naman practical sa pinas ang lowered.