Naples can ask for support for independence of other nations. The best case scenario is when both 奥地利 and 卡斯蒂利亚 rival 阿拉贡. 英格兰 and 匈牙利 can be just as good as replacements for Austria though, as Aragon only rarely rivals Austria. This will let Naples get a support independence treaty with any of these nations. Before starting off, the player could max out the force limits and ask for support for independence from Austria and Castile. Then they could improve relations with Austria. When the truce is over, the player could declare war. This will immediately call whatever powers have backed your independence (it is best to have 卡斯蒂利亚, 奥地利, and 匈牙利) In the peace deal, the player should retake Naples' Sicilian cores. Continuing to improve relations with Austria until Naples can join the HRE is a good idea. If possible, ask Aragon for cores back, as well as independence. Sicily is very important in expanding into Africa if one so chooses.
After independence, it's up to the player to choose where to expand. There are many options available due to Naples' size. If Naples joins the HRE, attempting to become Emperor is an option, although this has to be done before the shadow kingdom event to prevent the triggered modifier for staying in the empire. Another option is colonizing the new world. One could easily snap up a ton of North America as Naples but funneling trade to Genoa requires power in the Bordeaux node. A better expansion option may be Africa, trade from West Africa may be pulled across the Sahara to Tunis and on to Genoa. This path of expansion requires Exploration ideas, which can be dropped after bridging the provinces south of 费赞. Another path could be to expand into Italy and reap the riches of others, in this case claiming across sea zones to attack 锡耶纳, 热那亚 or 费拉拉 could be a good idea if 教宗国 has good allies. A French alliance is quite common with Naples so this could assist in Neapolitan endeavors. Releasing nations to diplomatically vassalize to prevent high aggressive expansion (such as 摩德纳 and 帕尔玛, or even 阿维尼翁 if the player is fast enough) might be a good idea. Naples may consider expanding eastward through 拉古萨 or 塞尔维亚 into the Balkans and 匈牙利, outside of the HRE and lead the crusade against the 奥斯曼, it is recommended to only start to do this after forming 意大利, as it will be difficult beforehand. Blocking off the Ottomans from their Balkan territories from the straits is an effective way to siege out quite a bit of their richer provinces, including their capital. Taking lands and releasing Byzantium is quite an effective way of gaining more cores. The Indian path is also easy to achieve provided Naples has swept through North Africa to the 马穆鲁克 faster than the Ottomans can get to them or Naples has already taking Suez from the Ottomans.