A321 flight crew reported during initial approach they had lost all navigational guidance and flew the approach visually and landed.

Narrative

I was reviewing the a/c status on my phone on the bus and noticed it had multiple MELs The main concern was the No. 2 IR system; No. 2 ADR system; CAT 3 single approach. I copied the MEL info and reviewed them with my first officer. The MEL for this in my opinion is poorly written and causes confusion. We misinterpreted the IR2 MEL and followed only the ADR 2 system inoperative. This MEL was done properly. The MEL as I recall asked for the IR push button to be selected off which the IR system doesn't have push buttons. All 3 Inertial Reference Units (IRUs) were on when we got to the airplane. I recall informing my first officer that with IR2 inoperative; we would lose internet connection. The WiFi inop Non-Essential for Flight (NEF) was also noted. During cruise; my FO noticed that the WiFi was working and said to me we have WIFI. This should have been our clue however all nav functions were operating correctly. My initial thought was 'here we go again with another incorrect write up. Now again all was operating correctly until we were below 10;000 ft on the ZZZ approach; when we had an ECAM message that IR2 had failed. My FO lost his primary GPS; resulting in about a 0.3-mile deviation left of course from what my ND was showing; and to further complicate matters his FD was indicating a level right turn. I asked for and we ran the ECAM actions and cleared the message. We continued because my side was showing correctly or so i thought. We were doing the ZZZZZ and on approach control. I think we were approximately 7;000 ft; when the approach controller reported that there was a Cessna at 12 o'clock at 7;500 ft. We were looking for the Cessna but were unable to see it. We got a TA with and a moment later; we received a TCAS RA with the command to level monitor vertical speed. I maintained the altitude as commanded; and we were clear of conflict moments later.I performed a visual approach to RNAV XX R into ZZZ; the ILS and PAPI were both out of service. While on base to final for XX R; my FO noticed that we were overshooting the assigned heading and altitude and brought it to my attention; I was aware but at the same time trying to reengage the appc mode. That momentary preoccupation caused this slight deviation. I then just disengaged the A/P and AT. On short final all my navigational guidance was gone and thought that we had lost the my side IR system; GPS reference; and nav guidance; and we couldn't re-engage the A/P or AT. I asked my FO to turn off flight directors and flew the approach visually. We landed safely and proceeded to the gate. We could have gone around and taken time to evaluate; however my thoughts at that time were sick aircraft; I will land and troubleshoot on the ground rather than risk life and aircraft trying to troubleshoot in flight.Cause: This particular MEL was unclear due to wording. Operative WIFI; loss of navigation signal; TCAS RA and preoccupation with attempting to regain automation helped to cause this issue.